Hope this helps, Let me know if you need more! :)
Q. What would be the best tool to use to cut out the T-visor? Preferably something I might have or something cheap.
A. Probably a Dremel fiberglass cut-off wheel.
Q. Should I do this before or after I paint?
A. Wait until right before you're ready to paint, or even after- you can always touch up the edges just before you mount the visor.
Q. I'm thinking of painting the inside black (a nice, non-toxic water-based acrylic). Pro or cons?
A. I just sprayed the inside of my two with black enamel, but if you're going to be wearing it a lot, you'll probably want to use something less stinky ;)
Q. Can anyone suggest ways to improve the key slots on the back?
A. Very small diameter dremel bit, define the corners with a jewler's file.
Q. Is it just me, or is the dent a little small? Can it be made bigger, or should I leave well enough alone?
A. Mmmm... the dent's 'should' be identical to the originals. ;)
Q. Can anyone post a picture of what a mystery helmet looks like with a RA FS?
A. I'm pretty sure Lynn has one on his Jango- I just cut mine out of styrene. With an RA stalk though, you'll need to dremel out a socket in the RF 'topper' so that it fits right. with only about 1/4" of the shank showing.
Q. When I finally get to this stage, what would be the best adhesive for the ear pieces?
A. On my two, I just stuck them on with 5 min. epoxy, but my helmets aren't handled much. For something more durable you could drill from the inside (carefully!) and anchor them with short, self tapping screws.