when you talk about dual cranks I have to think of this post:
But maybe you can do something similar to the picture, every crank can be of a different length and then you just choose the one you feel comfy with. (deliberately not saying anything about pedals hitting your shin, as someone will no doubt mention that. 
)
Though dual holes in the cranks I can understand. A few weeks ago I found out I have many dual hole cranks, it’s just that 150s I like best.
only if you cycle backwards 
@Setonix @PedalSprell @Wheelou, appologies if this has been posted before. Unicycle gearing Crank Length vs Wheel dia. Its only a guide as leg strength, leg length, fitness, terrain etc all play a part.
Out of interest I match up all my unes on there current set up, crank length vs wheel dia for the types of riding I do. First for road, then for muni and they all came out pretty well bang on.
Very useful if buying new cranks as you can compare the gear ratios of each size. 
Thanks @MadHatchetAndy. For me from 26" and up I prefer 150mm. A healthy amount of control on any surface. And mounting is the same for any wheel, just a bit higher for the 36". Occasionally I change to shorter cranks to get the feel and then decide to go back to 150mm.
@Setonix yes agreed, for muni on the 26/27.5/29ers 150mm is about right for me also, on the road, I prefer to drop to 125mm. One real benifit of 3 hole nimbus cranks, I can just move pedals. Expensive yes but 3 crank settings in one.
On the 24" 125mm muni 114mm road and on the 20" 114mm muni or 100mm road.
I wrote something on this subject a while ago (hope it‘s clear enough to get my point):
Bottom line: Currently, I can‘t just match the total gain ratio for all of my unis and be done. Depending on the wheel size I can, or can‘t ride a certain TGR (for a specific application, such as road riding).
@Wheelou of course it is what feels right for you on that uni and what your doing on it. It always amazes me, how the smallest changes can make a big difference to the way a uni rides. Whether its wheel dia, wheel weight, tyre width and profile or crank length.
yeah… with seat or without seat… 
@Setonix 
I will let you experiment with the no seat option, let me know how you get on !
I will stick to the padded shorts and comfy nimbus air saddle cover although I have just bought, what some might say is, “almost no saddle” haha, so your not that far wrong
Late to the party but 100mm on a 29 is lovely! 114 is a good size if you want a bit more hill climbing and control but have ridden 100s for gravel and road unipacking on a variety of 700c and 29" tires up to a 3" 1.2kg tire.
I had a set of 90/114 cranks made that are floating in the either somewhere, but it was the perfect combo. I’ve tried 75s too and they are fun in a very specific set of conditions or relatively flat urban commuting.
Yeah, the ultimate cranks for 29" would probably be triple holes with 75/100/125mm for everything from normal riding to steep hill climbing.
I would love to have 75/100/125 triple hole cranks if they were available. I feel they would be pretty versatile for many different wheel sizes, especially for road unis
I also think a set of 140/115/90 cranks would be great.
