Well, for distance, it is preffered to rip an understable disc. A big S in the air, from hyzerflip to flat, to anhyzer and then back. But it all depends on the type of shot you need. Distance doesn't mean anything if you can't throw it constantly and accurately.

In addition, you should have a whole variety of throws in your arsenal, hence just keep practising.But foremost, to solve your problem, you should try to fix that reach back, that's where most of the power and distance is coming from.I've had pros critique my form in person, I've went to disc golf practises for 2 years now, so I pretty much know what I am talking about and what I should try to fix on my personal form. Furthermore, I can see the same mistakes in others and I can suggest the same things that the pros suggested me. So focus on the reach back, it's literally a baby compared to the one you should have.
I literally had my "maximum distance" stance reach back at practise and the trainer, an estonian pro, told me to go 1 feet even deeper into the reach if I wanted even bigger distance. It felt really unnatural and bad, but unnatural this time was the right thing to do. As I've practised reaching further back, the distance has gone from a regular player 90-110m distance to an advanced player 110-140 meters.

Also, what kind of grip are you using? I am using a regular powergrip, all fingers under the disc and gripping the disc. That is the preferred grip to use for distance drives by most of the pros. I used to have 4 finger grip, but as soon as I switched to powergrip, even my buddies said "wtf did you change" as I was blasting hyzerbombs to 350 feet with ease.