im at the same stage now, boot floor out and about to cut out crossmember too.
i took the silly route and spent about 200 quid on new boot floor and side panels and the 4 strengthening beams - i laid them in and they hardly fit anyway, should have made my own sides up like you instead
anyway i got them now so will have to use them/ make them fit
quick question - how did you get the strengthening beams off the bottom of the boot floor?
not that i need to cos ive got new ones but was just wondering how to reattach them - weld on or are they just bonded/stuck/rusted on?
cheers, and great work btw, ive just been looking at mine for the past few days thinking why oh why did i start this job