Hi Marc,
first i must say you are doing a AWSOME job---- i have a Mig 15 kit also and am following what your doing with great interest--- mine is a AFS wing---

Have you seen the pics of the silver one for sale on BVMs web site ??? it has a hatch with a conceled latch system--- shall try to attach a pic---
If you go to http://www.bvmjets.com/ and go to turn key jets--- scroll down and click on the pic of the silver Mig 15--- lots of scale detail and ideas---- the hatch has inside cables you can just make out to pull the latches open from the inside---
cheers Jay.