If you're breaking crosses, going from a solid core like PSGD to a multi just makes your problem worse. I'm betting you're using poly in the mains? If so, you're likely better served using one of the newer, softer, thiner copolys all around and stringing like many of the pros do, with a few pounds less on the crosses. And lower tension, in general. There's an easily found story about Tim Henman working with Priority One to get more control AND a larger sweetspot by moving from more lively strings at a higher tension to less lively strings at a lower tension. I've found that to ring true in my own experiences as well, at least in larger headed (say, 100 sq in), open patterned frames.