To give you a sense of what you can get away with, I ran bergs on a Sportster with drop through baseplates and 220mm hangers
Things to note is Paris V2 baseplates are compatible with BN and Caliber II hangers, and they sit about 3/8” forward compared to Caliber II baseplates; lower angle baseplates will bite less, I never had issues with the 43° plates; and sanding the corner of the deck is an easy way to get a lot of clearance
Cutting the drop through slot bigger will help a lot for sure, just be careful that you don’t introduce cracks and use the biggest washers under the deck you can fit (I have washers with a flat edge that I really like because it almost sits against the baseplate)