Thank you, photos would be great. A doormat is a great idea. My panels are smooth but I can cable tie at the corners.
Here's my whole set up. Poor pigs thought I'd come into feed them and then had to wait while I took pics before they got their dinner. My favourite thing about this set up is i can have one half fleece and the other half filled with hay. I loved having all fleece but hated having to try and get the hay off it when it came time to wash it, but this way the pigs get their hay to forage in and can still have some comfy fleece.
The sides are folded up on top of the cage, when I open the left cage door I fold the sides over on to the top of the right cage, and vice versa, it helps stabilise the cage so the top doesn't cave in so I can only open one cage door at a time. (I hope that makes sense, not sure I've explained it well.)
This is the ramp, I was really lucky to find a door mat that covers the ramp perfectly. I chose to make a ramp that covers the whole area because i tried using the wooden bridges but my guinea pigs would always just jump over the sides and not use the bridge, even when one was really old and struggled to jump over the ledge.
This is the c and c grids that make up the ramp, i folded them at the top so there's a flat surface at the top of the ramp for my pigs to sit on, they love sitting there.
Hope these pics help you come up with a way to join your two cages. you'll have to show us the finished result when it's done.