In reply to CurlyStevo: It's been rock solid for me so far. The bolt goes through the web of the spike, and that's tough material. The griprest can't fold upwards because it's hard up against the end of the shaft. The slot of the griprest is a good, close fit on the spike - in fact it's a bit of a fight to get it on there the first time. It eases up a
little once it's been in place for a while, but it's always a firm fit. I'm sure that if you hit it with a 3lb lump hammer you'd probably do it some damage but I think that falls outwith the scope of "fair wear and tear" even for winter climbing!
I wouldn't want to fall on it, though, if that's what you meant by "bomber"?!
As I said before, given the non-availability of the Petzl griprest, if I was looking to modify an old Fly now I'd seriously consider spending £10 to see what I could do with the griprest for the new Fly. Judging from the detail pictures on the Urban Rock web site, it looks like it might be feasible to get it to fit OK.
If I was starting out and looking to buy new axes now I probably would look at the Quarks or Vipers, as well as the new Flys (which seem to be a very good price for what they offer over and above the old ones), but as it is I'm very happy with my old Flys with my modifications. I was quite tempted by the Vipers when Urban Rock were doing their £220 pair deal recently. A pal let me "test drive" his Vipers at The Ice Factor and they failed to wow me enough to make me want to spend the money, even allowing for what I'd have hoped to get back on the Flys on eBay.