my new proform 750 carb has clear sight plugs, do I set the levels to the middle of the sight plugs or the bottom?

 

If the sight plug hole is at the same level as a stock holley sight hole set it at the bottom as a starting point. You can fine tune the main jet fuel responce by adjusting the float height from there. Raising the float height a little will cause the mains to start fuel flow sooner. Flooding and fuel slosh bogging is too high of a float setting.
I usually run the secondary float height a little higher than just dribbling out the sight hole.

 

alright i'll check it against my other carb sitting in the garage for height, then adjust accordingly

 

I ran my Proform carb just above the bottom of the sight glass around 1/8 to 1/4 full. I've tried higher and lower settings but thats what works best for me. F-Bird is right you can use float levels as a tuning aid, it may take some trial and error. I just put a Pro-Systems carb on my car it it required a higher float level around 1/3 full..and thats what they recommended.

 

alright i have the primaries at the bottom and the secondaries a little higher and it seems to run alright so far, but i'll make fine tuning adjustments as I go. This carb is certainly a much more tunable platform than my old 850 dp holley was.