I purchased one set of silver MKS Monarch pedal extensions from Rivendell Bicycle Works along with the pedal spikes for my Clem. They came in the mail here the other day.
I referenced from the description of the pedal spikes as to how to mount them. It states to use a "3/32" or 1/8" bit---the smaller size (3/32") means a tighter fit, but the 1/8" is fine, and makes it easier to screw in. These screw in real easy with a
2mm or 5/64" Allen wrench"
After much aggravation and painful finger tips following these instructions, I decided to try using a 9/64" drill bit to drill out the holes in the outer part of the pedal extensions for placement of the pedals spikes. Sure enough, they screwed in better than I had expected. With this application, they do not stick out as far as the prior ones I screwed in following the original instructions. Yes, they are tight. They are similar in height to the spikes that came with the original pedals.
You might want to try one hole on one of your pedal extensions with a 9/64" bit and a spike to see how it works for you first before proceeding.
In the attached picture, the spikes on the right are per the instructions on Rivendell's website. The spikes on the left are done with a 9/64" bit. Notice the depth comparison.
I just wanted to share this with the group.
Kim Hetzel
Yelm, WA.