Those stock strings on the Hoyt's are a lot better than you might think... They're built right with BCY materials. Pre-stretched (very high tension), pre twisted, and served under full tension. Worlds better than "factory" strings of old. I have used a set on one of my bows for two years. I also use Winner's Choice strings, but don't toss the old ones. Keep them for backup. They are probably better than a lot of custom strings on the market.
Sorry for the thread HiJack. Sounds like you got it shooting - I was going to suggest a little yoke tuning. You should be able to make a 300 work, maybe even a 340 depending on your draw length. I have used the TT FC rest to allow me to shorten arrows up a bunch. Old school thought is that overdraws require stiffer arrows - I tend to disagree - as long as you're cutting the arrow shorter of course. I've shot .400's off a 6" brace Katera with OD at 73-74 pounds - shot amazing and tuned wonderfully. I would keep the 50 grain brass personally - that 150 grains in the front is long range magic.
Coop