As a follow up to this initial inquiry I'd like to share what I've learned in the hours since I originally submitted it. I found a copy of the F1 factory workshop manual on the Bevelheads site, but the information there was confusing, and seemingly incorrect. "Check with a gauge that the distance between the float base and the flange on the carburetor body is 4mm". This is technically impossible as the float itself is about 20mm in diameter, and even if it were to be forced all the way up in to the top of the float chamber there would not be enough room for it to expose only 4mm to allow for this sort of measurement. Pressing on, I found a datasheet on Dellorto's own website specific to the PHF36, which cites 18.5mm as the distance between the bottom of the carb flange and the bottom of the float chamber. A repost of the diagram and settings can be found on the Ducatimeccanica site here
http://www.ducatimeccanica.com/float_levels.html. What's confusing in this diagram is the 18.5 + 17.5 specification. I've never seen something like this. Often times you'll see "18.5 +- 1" or something to that effect (as in the range of acceptable values for piston ring end gap tolerances, but this is a new one on me. Does anyone have an explanation?
In the end I used 18.5mm specification. I had to fiddle with the float levels and stops quite a bit to achieve this specification, and while something didn't quite right with this adjustment (there's much less range of motion for floats, but maybe that's the way it's supposed to be) I set them up accordingly, checked to see that the needle valve is open with the float at its lowest level, and reassembled the carbs.
I have not yet had a chance to test ride it, to see if it fixed the huge flat spot above 4K RPM but I will do so this afternoon and report back.
-tj in los gatos