IFR next? ,(well maybe not in the Slingsby, lol)
I don't know, in many ways it's an ideal platform to read the road signs from!
Back to the original question......
Strangely enough they seem to fly the same whether they are on a Permit or C of A. Neither the aeroplane nor the air itself seems to know the difference.
A Luscombe on a C of A seems harder to sell than one on a Permit, but that's a refelection of buyer preferences. In the case of the Stampe I'd suggest that it's more important to have someone who knows and understands the type (and the engine) doing your maintenance. If you're intending to pay someone to maintain it for you I'd say it's essential.
One thing I've not seen mentioned is that you can't do Aerial Work or Public Transport in a Permit a/c (might be important if your plans include selling flights in a vintage biplane).