Specna Arms Edge Upgrades?

[Ragingrental]

This morning I finished it (only had to put the gun back together). I haven't got around to trying it out yet as I  want to get some deans batteries (adapter broke). Overall it was a bit harder than I expected but not impossible and an enjoyable experience. Putting  the gearbox shell back together was a right pain in the neck, but eventually it went back together. Shimming the gears was miles easier than I thought it would be, which surprised me quite a lot. I managed to fire off a couple shots before  the deans to tamiya adapter broke  and the gun indeed sounded extremely quiet other than for the noise the compression parts made, as well as having faster trigger response (duh). The only issue is that that the overspin still remains. I'll have to try chrono it once I get new batteries but I feel like it sounds a lot faster than 20 rps. Is it possible I could downgrade from 11.1v to 7.4v batteries to try counter the overspin and lower the ROF? I was considering trying buying new batteries first, but I'm not sure what new batteries to get as I am unable to know if they will actually fix the issue, so any input would be really appreciated. I thank everyone here for your advice and helping answer my noob questions.