This is not very difficult, first findout from DSA if the FH is silver soldered on. It should be Left Hand THread, find an old open ended wrench that will fit and you don't care to grind on, then grind it thin enough to fit the slot on the Belgian FH. If it is Silver soldered on you will need to sweat it off, I use MAP gas for this. If not you should be able to just take it off, you may also want to try a strap wrench, I try this method first. To install the short stoll well I think you can figure that out, just be care not to bend your barrel or the tines on the Stoll FH.