Something to consider - the P4M only ever wore three color schemes - overall Glossy Dark Sea Blue (with Flat Sea Blue anti-glare panel, to be strictly accurate) was the primary one. For a brief period a handful of P4M-1Qs wore overall flat Sea Blue, and another handful briefly wore overall flat black. When the type was retired, some six years after the navy changed to the Light Gull Gray and White scheme, the P4M fleet was still resplendent in overall Dark Sea Blue. During most of the period of the Dark Sea Blue livery, the wheel wells and other such spaces were also painted Dark Sea Blue. When the Navy adopted the gray and white livery the P4Ms, though they never acquired that scheme, did acquire that scheme's white wheel wells and gear. (Strange but true, and well-documented in photos.) David's Mercators represent this change by having Dark Sea Blue wheel wells and gear on the early P4M-1 and white wells and gear on the later P4M-1Q.
That makes it unlikely that anyone would want to paint the Mercator in any other color (like the gray one in the post above) unless one was attracted to what-if, fantasy paints. (Not that there's anything wrong with that, but they don't appeal to everyone.)
In either case, on the real planes, everything in the wells was sprayed with the appropriate color, so there seems no reason for a more complicated texture.
Well, I suppose one could draw in things like pipes and other bits of equipment, or add stains from fluid leaks (though Navy maintainers were pretty compulsive about cleaning up and fixing such leaks.) I guess that sort of detail might appeal to folks who like to go into spot mode while flying the plane, drop the gear and zoom in to peer into the wheel wells. I wonder if anyone actually does that? Unless a lot of folks do that, adding such detail to the wheel wells would just complicate the model and increase the load on the processor, possibly adversely affecting frame rates for those who don't have top end computers.
One might actually add those equipment items to the 3D model as well as the textures, but that would have an even worse effect on processor load.
When David and I were collaborating, we always avoided adding unnecessary details for that reason. We didn't even put in a complete VC - just the panel and items that a pilot would see while looking at the panel or outside, like the way real pilots spend pretty near all their flying time. Many of us have downloaded models that looked spectacularly detailed while sitting on the ramp, but that wreaked havoc on the scenery, or reduced the frame rate to slide show speeds in the air. David and I always tried to make sure that our models wouldn't ever do that, and I'll be surprised if David doesn't still feel that way. He seems to have followed the same pattern when he made the P4M.
Well, I didn't mean to ramble so - I just wanted to toss out a couple observations.
even after a few beers... I can barely reach the urinal nowadays...