In the mid 70's I modified a couple Simplex seatposts and alloy-rail Idéale
90 saddles such that they went together kinda nice I think. See:
They weren't rare collector's items then, so it wasn't blasphemy!
In case anyone might like to make one themselves:
The inner chrome nuts with the kept washers are the original Simplex parts. The bolts that go into them, with the heads out, are Campy from a regular 1044 NR post, chosen because they're the only 7mm x 1 bolts I could find - that somewhat odd size is the thread on the Simplex nuts.
The Campy bolt heads by themselves wouldn't have been big enough, due to the large slot in the rail (already there; I didn't enlarge it), so I made those "washers" you see in the jpeg. They are from the heads of some gigantic allen-head metric bolts that were made to take a 10mm allen wrench, so the 10mm Campy bolt head fits nice-nice. I turned the taper on them just for looks, and a gram less weight. I notched them to make tabs that extend down into the slot, so they keep the bolts from turning when you tighten the nuts.
Those of you who know the Simplex post will remember the parts that clamp the rails on a normal saddle are missing. They are normally riveted to the post head at the point where the smaller bolt/nut are seen in the picture. I drilled thru the post there, 6mm, and used the centerbolt from a front Universal 61 centerpull, with the head on the other side where you can't see, and the skinny 12mm nut from the front of some sidepull. (Campy would have been 13mm, but I wanted 12 so you only need one wrench to tighten all three nuts) The saddle is slotted there, 6mm slot just a bit longer than the amount of fore-aft adjustment I wanted; that's the only modification to the saddle. The head of the Universal bolt has flats that key into the slot in the saddle, so the bolt doesn't turn when you tighten the nut. That bolt comes with a larger-diameter round section just by the head, which I filed the two flats into. I think you have to shorten the length of that larger-diameter part of the bolt a bit, so it doesn't poke through the saddle rail and hit up against the seatpost, preventing it from tightening further.
I hope you've enjoyed this glimpse into the mind of an obsessed madman! (Actually that's pretty common on this list - one reason I like it here!)