I'm glad not to have to futz around with a v750 and sheet film anymore; I know that isn't helpful, so...
The v750 will give NRs with colour neg film, you can't get around that.
The only solution is wet scanning, and with 8x10 film that means using scanning fluid directly on the scanner glass.
Tape off three sides of the scanner, but not the top of the scanner, which is the calibration area; taping is not necessary if the fluid is applied judiciously and carefully, and that comes with a little practice.
You can dispense with the mylar at first, but as you get more critical of wet scans, mylar should be used, if only to protect film when rolling out the bubbles.