Well if you're open to modding . . .
You might want to have a go at removing the side window and making it more secure.
I'd suggest glueing it down
(bolts would probably be better, but it that perspex is very thin then it might be too weak and easy to crack when trying to drill holes in it)
For preference I'd use "UHU All Purpose Adhesive" it's clear, drys soft, easy to use and easy to remove from smooth surfaces.
Make sure it's the solvent version, the non-solvent version is just PVA glue in a tube.
Still use the clips, the glue is not so much to hold it in but to keep it from being lose.