Saw this while looking at penny farthings.
It’s from this website
Looks really cool.
I bought the 48" model. Changed the old style block pedals to lighter ones with pins and put a Nimbus gel seat and handlebar on. You sit very high up, it’s very heavy, and takes a bit to get used to, but when you do, it rides like nothing else.
I was about to say someone on these forums bought one after a bit of discussion, I guess it was you jona (though I daresay there’s others). They look amazing, I think I’d want to keep that old-timey seat though even if it means having to have a cushion under my bum though!
Are they free-mountable at all? Is it possible at all to ride it with that bone-bending seat? (I’ve heard riding a uni with a regular bike seat is nearly impossible without handlebars… Something about slipping off the front!)
Yes, they are fremountable. Took me awhile. Getting on top is easy, it’s heavy enough to stand steady. The problem is it’s heavy so it’s hard to get it moving.
As far as that hair-pin seat. It is beautiful. It is also the most uncomfortable thing created. I tried it on a bike too. Now it hangs on the garage wall.
If your toy fund allows, this is a good addition. Keep in mind however it’s huge, so it’s hard to carry places.
I was wondering how tall you have to be to ride the different sizes.
I’m 6’1" with a 34ish inseam. My 48 with 170 cranks and a nimbus gel has the seat as low as I can get it. Since getting my 48 I have wondered who rode the 60" Penny Farthings of old. 52" and 54" seem to be the more common Penny’s for sure. 
I have a 45" “big wheel” from 1982, made by the Unicycle Factory. Similar construction in terms of a heavy wheel with solid rubber tire. Rides very differently from a 36" with air tire. Great for swoopy turns and spins, but terrible for riding long distances. Let’s just say you are intimately connected with the texture of the riding surface. 
Yes, you can freemount them, ride backwards, one-footed, seat in front, etc. Wheel walking is a bitch though.
That’s it. I’m starting a giant wheel flatland display team. Who will be first to land a 45" seat whip?