I have a Bushy 16" H-bar and it's 7.3lbs. It feels balanced. My pencil barrel 16" Colt seems butt heavy, not balanced. I think a 20" H-bar would be barrel heavy.

I build custom rifles too. I have a bolt action .243, 24" Bull Barrel Stainless Fluted with scope, stock and bi-pod that weighs in at 17.2lbs. It is extremely well balanced, but very heavy. I find that off hand shooting the rifle should balance in your non-trigger hand where it feels comfortable. If it does not balance there you will string your groups vertically when shooting off hand. The heavy weight means you can't hold it like that for very long, but it will be steady.

Light weight is great if you have to carry it and can't sling it. Heavy weight are great for longer shots, awesome if you can use a bi-pod. Balance plays a critical role for off hand shooting.