I am considering getting a stock feedr for my 5HP 43-454 Delta Shaper, if I can find one at a reasonable price. I will be running stock for 1 3/4 and 2 1/4" exterior panel doors. Is there a rule of thumb for determing what HP one requires? I have looked at feeders from 1/4 HP to 1HP and there is a substantial price difference. Any suggestions?