i would be very careful with a heat gun - they can be brutal if used thoughtlessly, particularly on very thin vynil. Ladies hair dryers are far more gentle, and allow you to control a more gentle flow of heat into the vynil, although this process does take a few more minutes to affect.
there is an alternative to your edging issues, which would give you a whole load of extra work.....: you could take a mould off part of your cockpit, make a grp skin and trim that. This allows you to fold over all the exposed edges. I did this on the inner door skin, and the inner wheel arches (which on the crendon are a little less authentic, but rather easier to trim). Does take a bit of time to do though
crendon door skin test fit - Cobra Club Gallery