Reply to TT case problem

I wanna make case for Technics 1210 MK2 turntable. I have major dimensions (453W x 360D x 162H mm), but I need inside dimensions, especially for the sponge that will press against platter and keep tt immobilized so it doesn't move inside case and that tonearm don't touch the cover of the case.

I tried to find dimensions online unsuccessfully. Anyone have any blueprints of TT cases or knows how I could measure all of that with least possible mistakes?

Thanks in advance.