You are right, none of these programs open Perf Mems from G1000 to save them as VA76 performances. Part of the reason is that the performances have a different structure in VA, than in G.
Before Ocan Altug whote his UPManager program, a number of people were working feverishly trying to decipher the performance memory file format of the G1000. eventually, they succeeded, but throughout the exercise there was no help from Roland. It may have taken them 15 minutes to generate a documented file structure. The VA76 has not caught on enough for people to justify the same effort. I am sure, this is a small consolation to you, but lack of after-sale support is a known fact with Roland.
I wish you best of luck in finding the solution to this problem, and I hope you share it with us, if you come across any tools.