I ordered a set of 9" props for my P1 some time ago, tried them in January. I'm pretty sure they were 9045. I hesitated long because I couldn't find slotted ones to fit the original motors, but I finally have it a "shot" (took over a month with the delivery) anyway. The set of hub adapter rings were no good for anything, and I just drilled the hub hole larger. "Just drilled" is a short version, as I actually used two or three sizes of metal drill bits (the ones I could find at home), using them manually without the screwdriver and then running them backwards on the driver, to not let them chew into the plastic. I got them balanced, installed and test flight.
I liked the new feel of the P1! I sounded and felt like much bigger bird

I was driven to try 9" by the need to find ways to improve video stability with the plastic 2D gimbal, Walkera G-2D and SJ4000. Cheap props, didn't lose anything. I have no clear impression that the image became better, or worse. I did lower the pitch and roll gains, which helped a lot to reduce high speed vibration. Later on in my workshop test runs I noticed the props do vibrate. Well, manually drilled hubs. They weren't 100% straight and centered. Considering this and the low price the results were really good. But running off-centered props was not my thing, and the thick hub ate some of the shaft thread needed for the nuts (safety margin!). I didn't gain noticeably more flight time either. I changed back to the cheap plastic slotted 8045, but I will re-introduce 9" size one day! I had so good feeling about them.
The problem is still the same: what to buy for the original motors (shafts)? If I can see correctly, there are no plastic slotted 9" props in eBay. Well, maybe one auction item. Others are either carbon fiber, or non-slotted. I'd rather not try cheap carbon fiber, as I've read so much about their vibrations. And the added fragility. OTOH, I may be on the wrong course altogether when trying to find cheap and goood. I do know it is possible, but I have to search this forum for more specific info on good sources.
I'm also stressed about the shafts and compatibility and adapters... It's ridiculous that the hub or shaft size and type is often overlooked in the item descriptions! Say, I can order a set of four motors with ESCs, but the motor shaft is not mentioned. Crazy. And this is what I basically came here for, to ask how you fit bigger props, have you replaced the motors, are there adapters (sounds I don't want such additional things though) etc. Sorry for the long post, but I'm all in for experimenting on cheap gear rather than saying "why to replace anything, it works like it is". That doesn't really answer the question.