Or you could use a 100k with a 100k resistor across the lugs, giving you 50k, but with a slightly less severe reverse taper than a 50k rev log.
Hmm, I feel like I've seen that somewhere else on this page...

You could also use a 100k pot and put a resistor across it to change it to 50k, but this would shift the taper to be like a reverse audio anyway.
Yeah, the momentary on switch is a cool idea, and an easy mod on this PCB. What a neat project, I always want to give it up to Slacker but I know he's tired of it. I keep finding new ways to use it all the time.
I'm really liking my dual-use stomp switch, mentioned earlier in this thread. It can either be a modulation on/off or a "max feedback" stomp, both of which are very useful. Put the time all the way up, play a note, then stomp it in max feedback mode, and you get a feedback note similar to an ebow or real guitar feedback (or like the Boss Feedbacker pedal). You can play little feedback melodies rather easily this way. The modulation kill is equally useful.