You're lucky to have the easiest style of Boler
front bench to convert. Some Bolers don't have that extra "square" cutout in the frame where your Porta Potti goes. And then even some that do have that don't have the cutout already formed in the bench like you do. So you're starting from a good spot.
If you wanted to keep it simple, you could use the existing filler piece for a table. I've seen people support the table in a number of ways, including the following:
1) "Hanging" a support from the existing mini-shelf that the sofa back used to attach to, and then having a leg that is the same as the fold-down leg on the back table, or a support that slants back to the front wall of the trailer. This is nice because the floor stays flush.
2) Using an RV table-leg socket - one half mounts to the floor and the other half to the bottom of the table, with a leg cylinder in between that you can take out if you want to drop the table down or remove it.
Another thought is that you might want a table that is slightly wider (curb to street wise) than the current filler piece. You know how at home your table overlaps your chair - RV ones often don't because they are using a filler piece that has to be just the right size but you don't have to have that constraint.
There have been quite a few threads about this which have photos and ideas on different ways, so those might be a help.