JR isn't that important for the PF even with princeton offense(i don't play it much but when i do, my Pf works could and he has weak JR for the level i am playing).
But i won't put your SF down low, because the inside Skills a lot more important for the PF then his shooting skills, so a C as PF works better then a SF on PF in the maority of cases.
PS: i would test motion offense to, which sounds to me more effective for your team with your JS heavy PG, SF and not so strong shooting PF. Maybe even Run and Gun could be your choiche, because it focus more on the guards and less on the SF(and you'll notce your good big man in every strategy, maybe a bit less then with princeton but i think your overall performance increase)