Ive used some of mr tank a lots methods for my tamiya Centurion. Not all of it, I think mine was a quick and dirty one (and the Mk3 is slightly different around the Besa anyway) but anyway, it mostly seems to work. Its not as pretty as the above, but it might be a little easier for some people. I basically cast the bottom of the plastic one you get with the Tamiya kit, and use it as a framework to put the fabric on with PVA,with the frame attached with double sided tape. It gapes a little (I can probably fix that with modelling putty), but Ill try to put some pictures up on here over Christmas to show what I did.
Thanks to Mr Tanks a lot for his good ideas. That stuff to make the Acrillic work better with the material really worked very well.