RE: 3d
Hiawatha, I think your bow needs a bit more tuning as the flight shouldn't be that different to make you not use FP's for practice. Look at tuning(string, cams, etc), spine, FOC of the arrow as places to start. Due your paper tuning after you've done the mechanicals. Also what type of BH's are you using? I know some will shoot higher or lower but group, which is the mission to accomplish for hunting. I have found fixed 2 blades by Steelforce and Magnus have always grouped like my FPs out of a tuned bow. Muzzy have as well. Most mechanicals do as well. Although for some reason wasp sst group high and TH's group low from my FP's but they all group and the difference is less than 1" from FP's which to me means I have nothing to worry about practicing with FP's and hunting with BH's. I am sure your aware every arrow and head combo can have a slight change in flight as to why you test all your arrows...I do the same thing with this regard and then mark the arrows that offer the best group and flight for hunting the rest go into the practice pile(which is usually 3-5 arrows a dozen with quality carbons). Now when I practice I use only FP's and the arrows that don't make the grade for the quiver, all I want to do is practice my form and know my yardage. This can be accomplished without hitting the bull or stacking arrows. Of course when season is dawning I will practice with my actual arrows and fire each broadhead on each arrow into a foam target...not required but I have a ritual that must be followed. I then number the arrows and heads to where they fit into my quiver. I only say this to point I am just as methodical about wanting to know flight and what my setup will do as you are shooting your one BH on your arrows into a clay backing. I think you should be able to save those lost heads and practice with FP's but whatever works is the best. Good Luck!
I like 3d's for practicing yardage and just hanging out with other hunters. I am not much into the comp part as I shoot a bow to hunt with and just enjoy the time outdoors. I belong to a club that has both indoor and outdoor ranges.