Luka:
Look, since you ask how to make your own prototype caliper adapter plate, I started mine this morning and only took me 2 hours, it is simple:
This is the STOCK caliper plate & Metrakit Adapter (For 220 m.m. disc), so I know the distance I need from fork fastener holes to adapter holes:
This is the GILERA caliper and its plate, again with the Metrakit adapter, this is the combo I was using before, remember?
This is an stencil made of simple paper sheet (I made several until got the right one) and a fiber board prototype:
I spent some 15 minutes adjusting the fiber board prototype to be sure all the dimentions are right, next step is to transfer the prototype plate into steel plate...maybe some day next week, I will show you when finished.
This is an easy project, just get some paper, pencil, rule, a dial caliper and your parts....take your time...I'm sure you can do it your self!
Regards,