Your comment about shooting as good as the what you are going to get isn't exactly true. I had a $150 Bear Whitetail Legend bow that I had to shoot at multiple targets with because of breaking arrows. It had a $15 double prong rest and a $20 site on it and shot XX75's.

Even with an arrow not spined exactly right tight groups are still possible if you have good form, therest is set correctly, and your sites are on. Especially at only 20 yds you do not need perfect spine to be accurate to less than 2 inches.

You obviously have good form for the groups you are shooting with the bow turned up to inside the recommended wieght. The poor groups are probably the result ofshooting the bow below it's recommended draw weight. Five lbs is probably a min of 1 turn and maybe more further out than recommended. Which is a no-no with any bow. Yes, it will turn out that far. However, there's a reason they say 50 - to 60 lbs. Once you get below that weight the limbs are moving more than usual due to the bolt being extended so far from the riser.