I just replaced my Comet ramp with the Pinball Inc repro. It wasn't entirely straight forward. Might be old news for some folks since these came out like a year ago, but opi figured I'd document my experience...
Two places required rivets--the blue flash lamp bracket at the top of the ramp and the little protector for the early exit above the pop bumpers. I used a Dremel to grind off the lip of the rivets and then punched them out with a small screwdriver. I don't have any riveting tools, so I used pinbits.com press rivets on the new ramp. They're not as good as real rivets, but they're adequate for this job.
I had fitment problems at the entrance of the ramp. The new ramp is thicker than the original, and that's great, but it made things a bit difficult. I had to Dremel out a large notch in the lower left pop bumper cap to accommodate the ramp. I also had to shave off a bit of the ramp wall at entrance of the ramp to clear the left playfield post. It's a tight squeeze between the playfield rubbers, but it does fit. The thicker ramp entrance means the ramp flap isn't as flush with the playfield as the old one was. I could have sanded down the playfield where it meets the ramp, but decided I didn't need to.
The new ramp comes with a slightly taller post for the ramp exit, above the Cyclone ramp. I used it, but found that when I used the Mantis protector for the inside of the ramp, I couldn't get the playfield glass back on. I had the choice of either removing the Mantis protector or going back to the shorter post. I know the new ramp is thicker, so maybe I could get away with not using the protector, but I saw what the ball did to my old ramp exit, so I decided to keep the protector. I went back to the shorter post and the glass went on fine...but the ball got stuck under the Comet ramp when it went around the Cyclone ramp. I found that I could loosen the screw that holds the Comet ramp to the Cyclone ramp just enough to get clearance on both the Cyclone ramp and the playfield glass. That might not be the case if the Cyclone ramp is replaced as well.
Decals went on easy and look pretty good. I'm happy to not have to use the Mantis protectors on the ramp entrance any more. They did an excellent job and totally saved my old broken ramp, but they moved around sometimes and the ramp looks better without them. I'll save them and put them back on if this ramp cracks or breaks. The underside ramp exit Mantis protector doesn't fit the new ramp, but I don't think it'll be necessary anyway.
The new ramp looks and works great. I've got the Cyclone ramp and Boomerang subway on standby in case I ever need them. I bet these reproductions will save a lot of machines!