I have several of the NOE RG4 moulds with the Hp, Dp, and Fp pins. Not that I’m crazy about Hp bullets, but because the Dp/ shallow Hp are the most accurate in my guns. Maybe they stabilize the bullet, maybe it puts the weight where it needs to be, I’m not sure, but they work for me.
Casting with the Rg series has a learning curve, like most moulds. One thing I do to get a better bullet release when casting with the Hp or Dp pins in, is run them pretty hot until I establish a good steady rythme. I usually cast fast to start, and keep the first fifty or so bullets separate , and usually end up putting them back in the pot once I see how they compare to bullets cast later in the session. I like a large spruce at first also, to heat up the spruce plate and add more heat to get the pins up to temp. Another thing that has helped me get the bullets to release much better, is to polish the pins. I chuck one pin at a time in a chord less drill and polish the entire pin with fine steel wool and synthetic 2 cycle oil. Doing so has worked quite well for me, especially on the deep Hp pins.