Do NOT particularly concern yourself with getting the tips level.
Ask Roy how many odd shaped selfbows he's made with this method. Deflex in one limb, reflex in the other? Level the tips? Yeah right. Good luck with that.
Get the handle (the shooter's side of the handle) 'level' in the tree. In other words, make it such that the tree supports it how you want to hold it... not how it MAKES you hold it. Keep in mind, assuming in the end limb strength is balanced, you don't want the handle tipping one way or the other in your bow hand AT ALL.
Then draw it from your string hand's fulcrum point, drawing perpendicular to the handle, and gauge relative limb strength by which way the hook drifts from the line. It will drift toward the stronger limb.
The closer the bow's longitudinal center is designed to coincide with the string hand fulcrum the better. You can take my word for it, or I can explain in detail, but we'll be getting in pretty deep if I do :^)