All but two models of Hortons require the halfmoon or moon nocks. The barrel has what is called a "micro flight" barrel. When shot the arrow is not in contact with the barrel except for the last half an inch or so. If you look at the end of your barrel you should be able to see what I am talking about. After that first half inch you will see where the barrel is machined deeper then the end. Your arrow will sit in this when it is cocked and look like is will be there when shot. But as you shoot the string goes into the nock and lifts the arrow out of the barrel and thearrow rides on the front half inch and on the nock in the string, much like a vertical bow with a prong rest. This way you do not get defects in the barrel affecting your acuracy. If you shot the flats this design will not work. Will you be able to shoot flats? sure, but they will not group as good. Horton does not sell flat nocks anymore, they do this for a reason, and its the barrel. They dont just not sell flats for the heck of it.

Now as for you second question, arrow length. I do not think you will get a arrow shorter then 20" to fit on your bow. I think the only bow that will take shorter arrows is the steel force. Also if your goal is to shoot a lighter arrow to gain speed you will ruin your bow. Alot of guys try to get lighter arrows get a fewmore fps and then crack their limbs and blame the bow maker for bad product, and its their fault for not reading the print in the book that comes with the bow!Hortons minimum arrow weight is 431 i think but you will have to go to their site to comfirm. If you go lighter you will be putting your bow in a dry fire affect and crack your limbs after time.

As for theb-heads, I have shot all most all of my deer with 100 grain muzzys. But this year I will be trying the new tekan 2's. Goodluck and enjoy!