Can't release trunk latch?

The only thing you can try is have someone push down on the hood while you pull the lever to release the hood. You could use a pair of pliers on the hood release cable in the glove box to give you more of a pull. The only other way is by trying to get at the latch through the bottom apron pan.

I do not know much about the convertible frame, but in my 73 superbeetle I removed the front part of the frame so I could get to the underside of the spare tire. I then cut out the drain plug under the spare tire and then pushed up the spare tire until I could get my hands on the locking mechanism, I had to push it over manually while someone else opened the handle. I suggest the stronger of the two do the lifting, it isn't easy lifting the tire if things are on top of it. Once it was off (since I didnt have the cable to open it from the glove box) I removed the plunger thingy that goes into the locking mechanism so that the trunk could no longer lock on me. I only keep the flat spare tire and my trash in there anyways so I don't need to lock it.