Santa brought me a Primo seat post so I could tilt my seat up.
http://www.unicycle.com/shopping/shopexd.asp?id=602
Here’s a pic of how I modified the stock Miyata plate to attach the rail type seat post. The rods are 3/8" diameter. The post is further back than the original. By using the original plate, the much needed ribs are left on the plastic base.
Some weight savings could have been made by shortening the rods and drilling large holes into the riser plates.
Interesting cantilever design. It changes the geometry of the frame a bit, but that can all be adjusted for.
For the people who don’t have a huge 23" Apple Cinema display and a broadband internet connection I’ll attach a resized picture. 
Hmm - cantilevered.
If I were you I’d change that so it’s supported at both ends - you could add some more rod in there. the increace in stress through the cantilevered rods over ones that are supported at both ends is huge.
More importantly you are now puttting a cyclic bending load into the seatbase and the seat-post. Because of this, something, at some stage, will definitely bend or break.
