This has been covered before but not with any real definitive answer as you say.

I own an old Goldstar and have also asked the question about magazine compatibility.

I believe you can modify a new-style magazine to work in the old Goldstar.

I too have read about removing the indexing pin from the underlever but would never consider modifying the rifle to suit the magazine, would much rather modify the magazine to suit the rifle!

Cheers
Greg