Cool -

I think you would find it's easier than it might seem to slip the tube out.

The seat lug is thick as are the stay caps and it will take a good bit of heat to get that stuff to fall apart. If you focus most of the heat on the tube to be pulled (no worries about cooking it for obvious reasons) and let that heat soften the silver I think you'll find you can pull that tube without worry of dropping the stays off.

You can also put a heat sink in the seat tube (a crap post is perfect) and this will pull a lot of the heat away from the stays.

Best of luck to you - keep up the good work.

dave