Also, socket the clipping diodes and try some things out. There are a lot of different variations:
No diodes in first stage: more bass, but may be too much
LED's in both stages: more of a fuzz/hoof sound. Different color LED's clip differently. Red clip quickest with the least amount of headroom. green/blue/violet, the most headroom before clipping.
Silicon in both stages: traditional muff
No diode in second stage: louder more uncompressed muff, but may be too much
I landed on yellow LED's in the first stage and violet in the second.
I also have an Ungula with green LEDs in both stages and that sounds great too. Red were too compressed for me. But socket and see what your ears like.
Also make c10 .01uf for flat/not scooped mids... if you want more guidance on this, check out the kitrae large beaver mid-range switch:
http://www.bigmuffpage.com/images/schematics/1976_BMP_Schem_Mids_Switch_Mods.jpg
You can see that c9 and c8 (in this diagram... not sure exactly how they match up with the Muffin) need to be the same for flat mids. Personally, I think that flat mids are enough, esp if you don't want to put in a mids knob.