Yes be sure to leave access were the floor panels are!
We have a very well loved and experienced wood working busnut that used to be on this site that bought and built a nice Eagle. But when he bought it there was no floor in it at all! Just the cross members and even no floors in the luggage bays. (when arrived home with it he backed it in the driveway and his wife stepped in the steps and looked down and said "you could have at least bought one with a floor in it!")
Well he did a great job converting it, but he did not know about the access panels since he was starting with a blank canvas (or actually chassis!) and didn't know about this site at the time.
Well he did a superb job of building it and even put in a well insulated solid floor like 3/4" Marine plywood, 1/2 insulation, & another 3/4" flooring plywood all cris-crossed for strength and sealing purposes!
Well guess what first time he stopped by my place and needed a transmission hose replaced he looked at me like I had 3 eyes when I asked him how hard it was to get to the access panels under the bed.
His eyes glossed over and he asked "Access panels? What access panels?"
I explained to him that they all had access panels to get to the engine/trans and other service areas from the factory.
He again got a glossy look and said "AH, ain't got none!"
I asked are you sure. and he said "YES I sure as I'm the one who put the floor in there is nothing close to an access panel in it!"
Well it made the job difficult at the least but we were able to get a small wiry mechanic to climb in on the curb side and go through and over things until he was able to get on top of the transmission and take said hose off! The next evening he returned to my shop and put the new hose we had made up back on!
After that he promised the next time I saw the bus it would have access to he engine/trans and other things needed for future service!
Well next time he was at our place it didn't and this time he had a cracked exhaust manifold on the street side and there had to be access for the available mechanics to be able to work on it!
So out came the bedroom, and the circular saw and a sawzaw! (he now has a huge access panel!