Hi Alex
6 volt is giving 25% more power to the servo, and you have the +of the weight .
Its better to take power up then dead weight ,an you need the weight anyway !
The folding arms of your Andy can use that extra bit of power , and you need a bigger chute for the high altitude you are living in .
Bigger chute needs more power to puldown the arm .
When is your Andy arriving ?
,jules