Man, if I only had room to move my seat farther back and down.
The taller you are the worse it gets!
Maybe you could get Bacchetta to make you a custom extra-long aluminum or steel frame? (Rich Pinto already told me years ago that this was not feasible for carbon fiber frames with their production process. However, I did not ask about aluminum or steel frames.)
Maybe you could cut two Bacchetta steel frames in two at different points and weld the longer front section from one frame to the longer rear section from the other frame for an extra long frame?
Maybe you could get a custom extra-long carbon fiber Carbent frame from Bent Up Cycles? (You would know more about that than I.)
Here is a bike that I built in Germany with a custom extra-long Hi-Liner steel frame from BuS Velomo (who will not ship to the U.S. for insurance reasons) to allow for more seat recline:
Once you go custom you also have the option of attaching the rear axle to the chain stays at a higher point and running the power chain *over* the right chain stay instead of under it. This will lower the rear end of the bike and the seat. However, it will also reduce wheel/seat clearance and limit seat recline. You can regain that clearance by making the frame even longer but that will raise the seat again, thus reducing the net lowering gain. Another way to lower the seat is to reduce the amount by which the head tube sticks out below the main tube. This will lower the front end of the bike and the seat at the cost of giving up front caliper brake compatibility. (I chose neither of these options.)
If the front of the seat curves up you can make it easier to reach the ground, without lowering the seat, by cutting off part of the front section of the seat.
A longer frame will require two idlers, one in the rear to keep the power chain off the right chain stay and another one in the front to keep the return chain off the fork.
On my stock Bacchetta CA 2.0 frame I increased seat recline by cutting a slot for the wheel into the carbon fiber seat, thus allowing the wheel to reach into the foam cushion area, with only a thin slice of foam separating my back from the wheel:
As long as the Railgun seat has a single center spine it is counterproductive because it reduces rear wheel clearance compared to a conventional dual-spline carbon fiber seat. However, as I understand it, the Railgun seat does not curve up in the front, even when very reclined, thus making it easier to reach the ground.