Fitting seats - suitable load bearing position on chassis?

[marinegirl]

Hi

I'm planning to put a removable double seat in the back of my 2000 (not new shape) Smileyface SWB...
Any tips for how to check which areas of the chassis have sufficient load bearing capacity?
I won't be fitting them for a while, but it will make a difference to the overall interior planning...

Thanks in advance!