Wow. what a contraption. Mantra+Girvin+ suicide Spinerys. I love it.
Funny, my first thought when I got the mantra frame was, to build it with a Girvin fork. That carbon leg titanium spring version. But I just was not able to find one.
My selection of URT's, all Orange X1's in various guises and build states etc. Great to ride, loved mine at Mountain Mayhem a few years back, returning in 2017 with my X1 maybe even my X1RS
Sure, a URT rides differently to the modern virtual pivot stuff and are pretty much obsolete these days...but isn't that why we're on this forum in the first place?
Here's my selection, not adding much, but with some linkage fork loveliness for interest:
Ibis Szazbo:
Klein Mantra Pro:
And currently in bits: Breezer Twister
Of those, I prefer the ride of the Szazbo, but the Klein stops the traffic....
Also a couple more obsolete almost URTs:
Klein Palomino
GTSTS-1000 I-drive
My preferred pedaling style includes lots of out of the saddle mashing, ala SS style, so I find these URTs to be very efficient, at the expense of less plush descending.
Between my Schwinn Homegrown and Ibis Szazbo, the Ibis pogos more, as you can see the pivot is higher up than the HG and slightly further back; and seated suspension gives more pedal feedback on the Ibis, i.e. more swingarm rotation around that pivot.
All in all they're both hardtail-like when out of the saddle cranking, which I prefer. Cheers