Anyway, I had a bit of a win today with both my VTRs as both had resisted all attempts to remove said bolt/cap (whatever it's called) and the hex hole in the centre had been chewed out with a rattle gun on both of them (by me, I'm afraid to say!)
I managed to get one of them out (the '97) by using a dremel and making a hole in the bolt to fit a punch in at about a 45º angle and lots of WD40 around the circumference for a few days. After several attempts with a bigger hammer each time, an almighty whack, with the biggest one I have, got the b@stard undone. The cap was in a fair old mess but I was buggered if I was going to pay $30 for new ones + freight so have fixed up one of the battered ones with a modification to allow installation and removal. I drilled a couple of holes in the thickest part and tapped them for an M6 bolt then made up a plate that can be bolted over the holes and a 1/2" drive ratchet or handle used to do up/undo the cap

To get the one out on the '05 bike I had to carefully line up the plate over the cap and start drilling using the plate as a template having measured the one already out for the depth I could go to without breaking through the back of the cap. I was amazed that everything lined up (sort of!) and was then able to tap the threads into the holes. Because I have a Carbonadi cover on the alternator casing, I had to 'adjust' the plate to fit into the hole in the cover. Once off, I did notice I had just broken through the top of the threads by the o-ring so no harm done
Anyway, it worked and didn't take too much effort on the extension handle to get the cap loosened.
Heres one of the caps wher I've filed off the rough bits and filled it in with plastic metal.

So just got to get some new o-rings now and all done. Bothe the o-rings were squashed flat so suspect the caps were way over-tightened