Hi Ivica,
Thanks for the illustration, I definitely will not do anything that will permanently damaged the woofer.
Just for discussion, there are other fabric surround that may fit, I have seen it before. The picture I have attached in my previous mail is a case in point. It is twin roll, and narrow enough to fit the original foam gap.
Most likely I will experiment with bi-amping and power amps to get the sound I want.
Cheers.