What size cranks would you recommend for a 29" Road unicycle once I get used it? I ordered one with the standard 125mm for now. I am pretty comfortable on a 24", so now I’m looking to work on the 29". I use the uni for exercise and come across hills in my travels. I usually ride around 10 - 15 miles on the 24" if I have the time. I never used a 29" so I do not know how long it will take me to get comfortable on it. Any input will be appreciated. Thanks
Just ride with the 125s for now. in the future you might want to go shorter but 125 is a nice versatile size.
Double hole
Why not go for the Kris Holm 125 /110 double hole cranks?? Thats what I used before I fitted a schlumpf to me 29.
125 is totally versitile and you will get up most hills then quickly switch to 110 for the flat fast stuff 
I rode a 24" Schwinn for 40 years. Three years ago I got a 29" Nimbus with 125 cranks. When I first got on it was very challenging but I didn’t have to bale very much, just a big effort to keep balance. I got better at it every ride and within a couple months my skill improved dramatically. I do flats, hills and off-rode trails. I have never tried another crank size. I do too many hills to go shorter. Even when I am on the flats I seek out hills and bumps. I guess the dual hole mentioned above would be a good option for a quick change if you want to do a long flat ride.
Thanks - 29" crank size?
I’d like to thank everyone for the input on crank size. I expect to be challenged with the larger uni after hearing that one of you had a little troube riding one with 40 years experience. I am only riding for one year. I am 52 by the way.
Dont stress
Dont worry about it… a 29 is just a big 24 … wait til you try a 36!!! 
125s will be perfect. Once you get used to them, you will never change. They are just right for what you will be doing. Plenty of control, good speed, solid climbing capability.
I use 145s, but I do quite a bit of Muni as well.
Then again, going from a 24 to a 29 (trade descriptions - a 29 should really be called a 28.5) is a smaller jump than going from a 20 to a 26, and I’m now pretty happy on my 26 after less than a week and less than 2 months riding my 20!
good!