General Trying to use virtualbox to downgrade 6.1.6->6.0.1

[aPple nErd]

So i'm trying to do this because my iPod touch 4 ran way better on 6.0.x than on 6.1.x. seems like 6.1.6 completely kills it and i'd like to still use it to test out 6.x tweaks. as of right now, on 6.1.6, its unusable. is there any way to downgrade using win8.1 in virtualbox? it workes fine using ifaith until i pwn it. then it gos into a boot loop, or it just boots up like nothing happened. im thinking its a usb sharing problem between the host mac and the guest win8?

Any help is appreciated! thanks!