Originally Posted by Maelochs

Geometry is a non-issue because we are talking control surfaces, not the frame bits that hold them there.

Regardless of the frame geometry, the Rider's geometry is always the same.

You should have the same approximate seat/BB/pedals set up for all your bikes, and regardless of seat tube angle, that won't change. Figure out how far forward you want to lean and how long your arms are, and your favorite seat/bar drop, based on your other rides.

If you want the bar lower or higher than on your other bikes, or more or less reach, note that. Measure stack and reach---which are independent of geometry and based off BB and find what works on your other bikes. naturally there might be variation, but you will have a range, and based on your knowledge of how you sit on those bikes vs. how you want to sit on the new bike

It shouldn’t be hard to figure out about where you want the bars to be. Measure either seat tip to bars or from the imaginary line where the seat post hits the saddle top, to the bars.

Get a protractor and a ruler and a tape measure ... sketch up a rough drawing of your new frame. Since you know where the BB is, and where you want the saddle relative to the BB, sketch in the saddle. Then figure out where the bars should be, with the reach and seat/bar drop you like ... and then measure the length and angle back to the top of the headset (including any spacers you might plan to include.)

Or ... if the bike is together except for the seat, throw an old saddle on it, prop it up, lean into your riding position and look where the bards are and figure what you need. or pull a stem off one of your other bikes and estimate how much difference in angle and length you might like.