mike here is what i did. i used automotive putty. it is the same stuff auto body shops use for dents. this stuff worked great on my msh2. the problem i heard with bondo is that it does dry rather quickly and will sometimes crack. i have never used it so i can't verify it. but this stuff i used (bluish green in photo) has no air bubles and no cracks and worked great.
Bondo is automotive putty...at least that's what it's largely used for. Bondo is just a name brand, there's lots of off brands which are similar. Bondo is two parts that when put together appear pink...and IMO the advantage of Bondo is that it dries fast.
the stuff i used is one part no mixing. but it does need time to dry. at least over night. the advantage is that there are no air bubbles, no mixing, no mess, and smooth as all get out. you can get it at NAPA. check the gauntlet dart thread as the name of the stuff is there.
In hindsight, I might not have used Bondo. Not if there's something that actually dries more slowly. I wasted twice as much filler as I used because it dried up before I could apply it. You'll have seriously less than 5 minutes with Bondo. It does work well, mind you, if you can manage to work quickly or can afford lots of it.
Heads-up: the label says that this stuff causes cancer if the fumes while hardening are inhaled, or the dust while sanding.
honestly, their is a rumor about everything. I keep hearing how bad the rubies helmet is even though mine looks proportunatly fine. Their is a war about if Rub n Buff actually dries. I haven't used bondo myself, but my dad fixed a dumptruck where he used it and their was no cracking.