would reframing the kite to lighten it up change the way it flies, better or worse? Would it be worth it?
Assuming you are going to use a readily available frameset (Skyshark) it is going to cost you around $50 to buy the rods, and you'll probably need to buy nocks, ferrules, leading edge fittings and T-piece too. So it could cost around the $70 mark. Just on a cost basis I'd say it probably isn't worth it for a Silver Fox, especially as the benefit is unknown at this point (no-one seems to have done it).
The Silver Fox range are all framed robustly (i.e. can seem like tanks in lighter winds), but they are great kites to hone your skills on.
If you have a significant number of days when the SF struggles in the light winds it would probably be a good idea to look around for a dedicated light wind kite. A quick look at the forum earlier this year will show you that there are many to choose from and plenty of different opinions as to what might be a good one. Good luck if you go down that path!