This is no help to the OP but I had a fx gear frame made with an long "L" shaped rear dropout, not a track end. The slot is closed in back and runs forward and slightly down, then opens at the front down. This enables the wheel to be located anywhere along the slot so I can (and do) run cogs from 12 teeth to 23 teeth without messing with the chain. (A 24 would work but I Have yet to find one.)

I am a road fix gear rider and I have zero use for track ends. Road chains get dirty. Road dropouts make it far easier to pull and flip the wheel and doing it keeping one's hands clean is child's play. (Not an issue at a velodrome. They are near hospital sanitation clean. So are the chains on the bikes.)

The bike that inspired this bike was a Reynolds 501 sport Peugeot. A blast to ride fixed but the horizontal drop was so short I could just barely get a 2 tooth cog difference and 1/2 links were required to get the chain length just right to do that.

"L" shaped dropouts angled 11 degrees (a compromise between rim brake track angle and horizontal to not affect BB height that allows the brake shoe to stay on a semi deep Velocity Aero rim) are cool. I highly recommend them!

Ben