I'm looking at the ork for the Proline 4" Patriot. The ProLine Patriot 4" model has a 12" MMT. You said yours is 6"? That would make for some short root chords on that Patriot. Seems like it would look odd. Who's the manufacturer?
In the Proline model, looks like the distance from nosecone shoulder to top CR is about 28.5". Targeting 12 psi would need 2.2g 4F BP. If you put a 3rd CR at the top of the MMT tube, you can shave off another ~4" in your charge calculations. That drops the BP to about 1.9g. Either way, you'd need to supplement the charge that comes with the motor. I supplement all the time when I fly my 3" scratch built rocket in single deploy. Just sprinkle the extra BP on top of the existing charge and slap some duct tape on top to hold it tight. Most motors come with ~1.4g of BP. You'd need to have a MMT that is 6" longer with a CR at the top to cut the inner volume enough.
Then again, if yours is just 6" the airspace inside is about 34" long, so you need 2.6g BP. Still not bad. Dump 1g on top of the motor and tape it down.