I'm posting this in Safety Razors 'cuz that's what I'm using! I took a Feather AC Pro and trimmed it to the length of my Merkur Progress. Then I put it in with the back edge resting against the posts and tightened it down. The blade was clamped between the base plate and the cap. The other side was empty. After trying a few different settings, I've found that setting it to 5, then continuing past to 1 (I call this 5+1), I get a superb shave! This set up feels very safe. I THE smoothest shave ever, with NO irritation. And it lasts a good long time. Usually when I'm done, I've got some roughness that smooths out with the application of AS balm. I've always figured this was my pores complaining. Well not with the Feather AC. I started by trimming a ProGuard with a pair of tin snips. No good! The layers curled under the shearing force and there were nasty corners sticking out. Then I tried using my Dremel with a cutting wheel. They layers didn't curl, but they still separated. So I switched to the AC Pros. I started at a low setting and didn't get great results. I 99% sure the edge doesn't extend out as far a DE blade so the exposure is very low. I worked up to the 5+1 setting. I tried 5+2 this morning and it was a bit too much exposure for me. Still had a great shave, but it was a bit more rough and I got a few nicks. I think this is poor man's Cobra but less aggressive and adjustable. I'll give the Super Pros a try too.