VERY interesting! I think I'm going to try this rear support post first. Then if unsuccessful, I'll go with the (hidden)access hole.
Meanwhile, I'll have to postpone this project till I address an immediate and more urgent "issue." My Norcold will have to be replaced. Something in the rear components burned last night. Oh the "challenges" of motorhoming... But what else does an old man have to do when it doesn't take all day to count his money!
Rush
PS: Thanks for all your advise, and I'll check back after I'm released from the "ward."