I'm 6'4".  Will this help out my "knees rubbing on dash" problem?

Try putting the books on your seat and see if that helps. If you need more lift, I can make you a taller riser for the same price.

I'm 6'4".  Will this help out my "knees rubbing on dash" problem?

It will make a huge difference. I was getting leg cramps and it took care of that. The seat will fit you better and you would notice a more comfortable sitting position.

I had to build a seat riser so I could use my Zforce so now, I build them to sell.

https://www.ebay.com/itm/CF-MOTO-Zforce-2-inch-Seat-risers-manufactured-by-LUCKcraft-metal-works/324068389539?hash=item4b73fb32a3:g:zhUAAOSwDYNeQMll

I had problems with the seat position in my Zforce from the day I picked it up. Long rides created leg cramps so, I built a seat riser and now market them.

https://www.ebay.com/itm/CF-MOTO-Zforce-2-inch-Seat-risers-manufactured-by-LUCKcraft-metal-works/324068389539?hash=item4b73fb32a3:g:zhUAAOSwDYNeQMll

Looking forward to learning a lot about CFMOTO. Recently purchased a Zforce 500 trail and love it. I still own a Polaris Ranger but it's for sale. I've owned about every brand except Can-Am and this CFMOTO is a very high quality build.