ok...
Your guy was using the AMO standard.
That standard is to measure your actual draw length (DL) which is from the deepest part of the grip to the string..THEN ADD 1 3/4".
not sure why amo does this..I think it's to help in arrow length so the b-head doesn't hit the shelf.
I really don't like that standard...really confuses many new guys..my self included.
You can understand why with a true 28" draw a "no less than 29" arrow just wouldn't clear the riser with a b-head.
Sounds like your actual draw might be about 26.25" (28-1.75=26.25)
Around here, talking actual draw is the norm. don't know why..but it is..lol
Again..I'm very surprised those arrows are flying straight for you.
They should be way stiff.
I'd do a search on paper tuning. ...Basically shoot through some thin paper like news paper from about 5 foot away. Look at the tears. If you're getting "bullet holes" with an "x" from the fletching you're good!
If the paper tears in one direction or the other tuning should be done.
..doesn't need to be a fancy setup for the paper buddy..
I just put a 2x4 between a couple stools. Staple the paper to it. And put a couple squeeze clamps on the bottom of the paper to hold it down.
I'm afraid you'll see some funky groups when you screw in broadheads.
you're total arrow weight must be around 455grains with the 140 point. If your bow is 55# at 28", you're probably holding about 51#. That gives you around 8.92 grains per pound. (455/51)
The norm is around 10-11gpp. Shooting lighter can add quite a bit of vibration and isn't the best for a bow. You not super light though. I'll bet if you went to big Jim's site and bought some 200-250+ grain tips you'd be happily surprised at the difference. That would get you to about 515-565 grains or 10-11 gpp.
http://www.shop.bigjimsbowcompany.com/Standard-Field-Points-Dz-BP702.htm If you're happy COOL! I might be way off here bud.
just trying to point ya in the right direction.
HAVE FUN!!!!