I just bought a Drenalin(sold my other 2 Mathews this spring)and Nick set it up for me since I dont have a press yet.He shot it and hit 1"square at abut 15 yrds then handed it to me to shoot and lo and behold hit it just about dead center on one shot,Iam 5'11" and he is around 5'9" not bad for not shooting a compound in about 9 months due to RC damage...Its just like riding a bike,you never forget how.....
Draw and how you hold the bow are 2 of the bigest things,due to the fact that the distance between eye(center of peep)and nock dont very much from person to person at around 6" so that really shouldnt be a issue at 20 yrds,the issue in my book comes if you are pushing the bow out on release or just letting it drop(canter)forward witch is why you use a wrist strap....
Pushing the bow out while shooting can cause a unwanted canter in the bow witch will give you differant shot placement.(this is all with a mech release)if you shooting fingers then thats a whole differant can...