black tank help

[pgheald]

Hello everyone, I have a 58 SS clipper that I am doing a complete restoration on.
It was a park model and did not come with tanks. It has a rear corner bath. I would like to keep that configuration because of corner tub/ shower and window placements.
My problem is the black tank design/location. I've noticed some airstreams have the same corner bath and use an above floor tank. The new ones I see are smaller than I want which is not an issue because I can get a custom tank, run it into the closet, etc to gain more room. My concern or issue is most tanks have a shutoff right at the tank before the waste plumbing. I'm not sure how to accomplish that in a bottom drain tank. If you don't have the shutoff right at the tank couldn't solids fall into the drain pipe and clog it? Would I have to make a hatch in the side of the trailer to access the valve?
If somebody out there has a rear corner bath could you tell me how your system works? photos?
Has anybody modified the frame to get an in the floor black tank into the corner bath?
Any help would be greatly appreciated! I'm kinda stuck on which way to go!

[pgheald]

has anyone out there used the macerating toilets? Because of their smaller discharge I think they would work for a below the floor tank in the rear of my trailer