If you are cruising at 80+ that is pretty good. But if you are riding around at 60 to 65 then that is a bit low for sure.
I have everything stock except for a set of Long shot exhaust pipes. I was getting mileage like 32 to 34 mpg so I looked into the jetting and found the PO had the carb set up way rich. I found I have a Dyna needle after I put either the 164 or 165 mikuni main in it, I don't remeber which it is. I dropped the needle one adjustment at a time to the 2nd clip from the top. I am getting between 45 and 50 mpg if I ride easy and keep it under 65. However it made it much more cold blooded when it is a little cool out.

I don't have any back firing on decel so I don't think it is too lean.
I have also put the iridium plugs in and they do seem to make a little difference in power.
Hope it helps.
I am not suggesting you should mix manufactures on your jetting. I think you will probable do better if you stay with the same company when you change jet and needle.