I just now stumbled across this thread.
We have the same issue.
The table legs must be folded each time we move
It's a PITA and since we don't use it as a bed totally
a waste of time since we have to put it back up as soon
as we get to our destination.
I bought a table hinge bracket kit like this--
Table Hinge Bracket Kit
but COULD NOT USE IT due to the window being too low
on the wall. The table hinge needed to be mounted on the
wall at a certain height and the window was in the way.
(I now have a table hinge bracket and table leg for sale ˘heap.)
I thought about purchasing/making some clips and
screwing our existing table legs to the floor so it can stay there
when we're on the road. I might simply drill holes
thru the existing table leg feet and screw it in place.
So far wife has nixed that idea and to be honest she usually
man handles (woman handles!) the table while I'm setting
up/tearing down outside.
I can't tell you how long screws you need but if
I fasten mine down I'm gonna use screws that only penetrate
the floor by 1/2".
If you come up with a better idea please let ME know!!