if your getting 5-6 gallons and your clutch isn't worn out please tell us what you are using.
slipping is when the shoes are very worn and small, the motor will need to rev high to try and get the clutch to engage, at that point to you are usually down to the springs touching the bell also...bogging is when the clutch is too early or below the rev range the motor needs to make enough power, it can also be a tuning issue.
If you change the shoes do springs and bearings also, if the inside of the clutchbell is uneven replace that to if you can't dremel it back into shape.
dropdown wheels is just a personal choice and i doubt you would notice the weight