Yes, it's back there, underneath the landing deck. I can probably go back and try to find the original part on that one auction block (a very tiny needle in a very big haystack).
The 1/537 scale vacuform mod kit by
Sci-Fi Spaceship Miniatures had it there (not a caonical source, I know) and the Eaglemoss model has
something there but it's not painted red like I expect it should if it were an impulse engine, as with other EM ships. Several fan-made meshes have that area lit up as if it were active impulse engines (also not canonical). Here's a good example:
View attachment 33214
The original piece I saw doesn't look exactly like that, but it's close. I found one image from the TNG remastered BRD set and that area is stupid-dark:
View attachment 33215
Apologies for hijacking the thread like this,
@JSnaith, with something not related to your project (maybe tangentially, at best). I'm somewhat passionate about the Soyuz class, as it's my top-favorite Miranda mod that has probably the least amount of background information and source material about it.