Well, itās been a while since there was an update on this model and thereās a couple of reasons for that 
Firstly I had to lay out the UVās in various UDIMs and do some texture tests to figure out the resolution I was going for. Initially I thought that 4096 would hold up with 6 UDIMs but it did not do so at all. So in the end we decided to go with 6x8192 tiles which holds up nicely from the pilots perspective. Should there be any close-upās needed itās easier to make textures specifically for that shot.
Secondly and most importantly Iāve switched renderers to V-ray and ditched Mental Ray for a number of reasons. Most importantly are render times since when Autodesk took over Mental Ray and made it standard in 3Dsmax theyāve stopped optimising it pretty much over the years. This means that Mental Ray as an āout of the boxā renderer in 3Dsmax, while it gives nice results, is pretty slow.
Now granted that Iām still figuring out V-ray (last time I used it was around 2008 I think) and Iām still optimising the settings, Iāve already greatly decreased render times.
Another reason for switching is that Mental-Ray, because it uses Maxās standard interface, has a very convoluted way of setting up shaders that use Multi-UDIM textures. You basically have to make a comp material and set the offset for each UDIM seperately, which is a huge pain in the b*t. Couple that with the fact that using multiple large maps really seems to upset it in both render times and memory usage.
V-ray uses the simple <UDIM> way of setting up things, you just link your texture and instead of COL_1001.tif you just use COL_<UDIM>.tif, disable tiling and voila, it works instantly.
Lastly, more and more studios (and thus more and more potential employers) are starting to use V-ray or are already using it. So from a personal development point of view itās good for me to also learn new things 
Iāve also started texturing obviously and so far Iām putting in the basic COL map (clean version) with all the dials etc. in. Have got a basic SPECR and also OPAC for the glass.
Nothing fancy yet but itās starting to look ok 
Keep in mind itās basic textures and Iām still figuring out the quirks in shading etc.

Cobra 6