About ten years ago I went through stretch where my arrows were showing weak like yours. I moved up to about  to around 80#+ out of a 55# bow and they shot ok, granted at 15 yards or so.

After hunting season, I quit shooting for a few months.  When I started up again those arrows were tailing off to the left at twenty + yards.  I ended up shooting 65/70 out of that bow.

I am convinced originally I was getting false weak results because of something in my form.

Strange these should be too stiff.  I'll back down point weight and concentrate on release.  85-90# should be right.  These are 95-100#.  Might even go to 160 grain Snuffer weight with these hardwood arrows.

Ok, with good form and follow through there is a slight nock wiggle up, but arrow burrows right on the spot.  Would dropping point weight 30 grains help?  Or shortening arrow a smidgen?

I meant nocking point/arrow nock. It sounds like that fixed it if they're not tailing though.

As for the slightly slower speed, I can't tell the difference unless I am shooting from 40 yds or so, where I can notice the arrows dropping more than expected. I wouldn't worry about it. Just be consistent.

The effect of silencer position on spine is real, however. Especially when using a bow matched to shafts that are right on the border of being too weak. Often moving the silencers to the string nocks will indicate you got a batch on the low side. With some batches it makes enough of a difference that I always pull out a bow square out at the truck and check my silencers right after checking my brace height.

Actually, each year when satisfied with setup/tuning, I even record silencer position right along with my brace height, arrow length, string length, point weight, and point-on distance.

I mean, in my mind, if I'm going to go through all that work to tune, I might as well remember it. Then there's the problem with getting silencers snagged on brush while hunting and needing to measure to place them back.

Took the 190 grain tip off and tried 160 grain on these 29 1/2" 5/16 95-100# Leopard wood arrows 4x4" banana.  Bingo.  When I focus on release and follow through it disappears in the soft center.  Total weight just a smidge under 750 grains.  Guess I'll have to use Snuffers with this group.  Plan to get a couple dozen 85/90 Tapered Cedars and Red Balau Rat Tail tapered for my VPA and Grizzly Instinct 190 grains.

One final tweak, put PC at 1/4 from top and 1/3 from bottom, this seems to work best from this Big River D/R longbow 60" 66.5# bow.  Shooting in the dark helps with focusing on the sound, arrow flight is as good as it has been.  Think I'm done!!!

Awesome! I may give shooting in the dark a try myself.

I leave the side door to garage open so there is some light on the target, then step back into dark along the house 10/12/15 yards.  The privacy fence and house make a good test tunnel.

Seems to be tuned.  4 arrow group at 13 yards.  Red nock of arrow number four tucked high right.

Tried L/6 and L/10, with "L" being length of string from touch points on each end.  Shooting 2315 @92.1# spine and 2219 @93.5# getting good arrow flight and a decent tick up in arrow speed over 1/3-3/4 silencer placement.  Noise is equal or less.  Think this is the spine weight I need to be shooting.  95/100# Leopard wood shooting off (poor flight) and low.