Why am I doing this?

I know I have a reputation as being a bolt-counter and very hard-nosed about precise scale accuracy. That really is not the case, and in this instance, the reason for making such precise measurements is because I am concerned about kit compatibility. As I said above, I wanted to replace the engine access grate on the UM kit, and I wanted options. So I am presenting this information for those of you in similar circumstances. Keep in mind that for me, personally, the overall look of the engine deck is most important, so things like amount and sharpness of detail and molding quality are more important than precise scale.

Measurements

The diagram above shows four measurements: 'A' and 'B' are the length and width of the entire engine deck (flat plates only, not the angled plates on the sides); 'C' and 'D' are the length and width of the access grates. A couple of notes:

• I measured using a steel ruler and my eyeball, so I estimate my margin of error to be within 0.2mm.
• Several kits were difficult to measure due to thick panel lines.
• I highlighted in red those measurements that are off 1.0mm or more for the engine deck, and 0.5mm or more for the access grates.
• I added the errors for the two measurements for the overall engine deck, and separately for the access grates as a general measure of overall error.

Evaluation

Manufacturer	Scan	Comments
Armourfast		Very heavy panel lines and shallow detail. Keeping in mind this is meant for wargamers, it's really quite nice in that regard. But probably not suited for a super-detailed display piece. The cumulative error of the engine deck is one of the largest, though the access grate is not too bad. The very shallow detail on the grate slats will make it difficult to realistically paint.
Dragon (early)		The molding and detail on this kit is the best of the bunch. The cumulative error of the engine deck is not bad at all, though the dimensions of the access grate are not as good. The detail of the slats within the access grate was oversimplified in this release of the small-hatch M4A2 hull.
Dragon (late)		The molding and detail on this kit is the best of the bunch. The cumulative error of the engine deck is not bad at all, though the dimensions of the access grate are not as good. The detail of the slats within the access grate was improved in this release of the big-hatch M4A2 hull (the Red Army kit).
ExtraTech (brass)		Its cumulative error places this piece in the middle of the group for overall accuracy. Etched details are pretty good. Given the specific dimensional errors, this part could provide a perfect replacement for the plastic grate on the Extratech plastic kit (for which it was designed), as well as a suitable replacement for the Italeri kit. Using it for other kits will require a little tweaking of the plastic deck.
ExtraTech (plastic)		Aside from the fact that there may be minor differences between the M4A2 and M10 engine deck sizes, this deck has the largest cumulative error. For the access grate, it's about middle of the road in size, but with very shallow detail. Probably why a replacement etched part was included in the kit.
Heller		This kit is one of the most accurate in all dimensions. The molding and detail are also one of the best, though the relief of the slats in the access grates is not very deep, complicating the painting of the kit.
Italeri		The molding and detail of this kit are very well done for a quick-build model. The engine deck dimensions are excellent, though the access grate is towards the poor end of the spectrum. Note the hatch handles should be on the rear of the grates, not the front as they are molded here.
MR Models		Superb molding and detail. Dimensions of both the engine deck and the access grates are some of the worst.
Tracks & Troops		While the length of the access hatches is spot-on, they are significantly narrower than they should be, which seriously limits the utility of this piece. You'll need to modify the frame around the grates with plastic strips in order to successfully use this piece with most of the plastic kits.
UniModel		Rearmost armored plate is split into two, and the line needs to be filled. Very shallow detail in the access grate. The engine deck dimensions are pretty good, but the access grates are some of the worst.
Zvezda		Most accurate piece in this lineup. Almost perfect in dimensions. Molding and detail are superb, but with very large locator holes for the separate details, which may be difficult to hide.

Summary

Overall, the majority of these parts look only so-so when built. Although the information above shows many dimensional errors to various degrees, most of them are within acceptable error for me (UM and T&T being the stand-out poor examples). The main problem with the appearance of most of these is the very shallow molding to the slats within the access hatches. Do I paint these areas black, and then drybrush across the slats to highlight them? Or do I paint the entire grate the vehicles base paint color and hope that a very dark wash will highlight the slats?

My dismay came when I had intended to replace the poorly-detailed plastic UM access hatch with the etched part from Tracks & Troops, only to find that these two pieces are very out of whack, but in opposite dimensions, meaning that the replacement wasn't happening. As you will see in the construction review of the model when I finish it, is that I ended up cutting the Italeri engine deck from the rest of that quick-build hull, and using that on the UM hull instead. After careful sanding and trimming, the new part looks very fine.