This is probably an idea that somebody already had, but I did a search and didn't find it, so here goes. I have a Muhle R107 razor that I like, but as my "skill" has progressed, it was dropped from the rotation because it seemed so mild. A while back, I saw a thread about using a shim to make vintage Gillette Techs more aggressive, but there wasn't a mention of what was used for the shim. So I started looking for thin materials that would make a durable shim. Then I thought, why not use old DE blades and just cut off the edges? So I did.
I used some old Feather blades. I trimmed off the blade edges with a scissors, then used sandpaper to smooth any rough edges. Multiple blade shims allowed me to experiment with finding the blade exposure that I would prefer. Three of these shims give about .5 mm of additional blade exposure.
The results seem good so far. Hey, it's something to try, and it has put my Muhle 107 back into the rotation again after many months of storage on a shelf.