There are several approaches. BTW, I'm assuming that your post contains a typo and that the measurements are cm and not mm as implied by your conversion to inches.
- Scan directly on the glass using the 8x10 film mask. This will work, but there may be issues with Newton's rings.
- Use thin, stiff, black construction paper to create a sandwich "carrier" that has a windows sized for the 65x105mm negs and an outside dimension to fit the v750's 4x5 negative carrier. The paper needs to be thin to avoid focus issues and stiff to avoid sagging.
I've used both methods to scan old format film that doesn't fit my v700's standard carriers (35mm, 120/620, & 4x5). I prefer method #2, particularly when I have a number of images to scan. I've created L-shaped "extension" sandwiches to fit 116/616 and 112 size negs (roll films larger than 120 & 620, but smaller than 4x5 sheets) into the 4x5 neg carrier. You will have to disable EpsonScan's auto detection of image area and manually select each image as the auto mode assumes modern image sizes appropriate for the carrier it detects.