Yes, you can cut the top off, but try to limit your pruning at this time to a tip prune. The plant will appreciate you're leaving its photosynthesizing machinery (leaves) intact until early next summer. The tip prune will force the tree to back-bud and funnel energy into existing branches and into creating new branches, which will help your plant fill out. You CAN root the plant, but it will root best if you include some of last years wood on the cutting, which might mean you'd need to cut off more than what's best for the plant (to get the old wood). If you make a cutting, stick in a sterile medium (like rinsed perlite, screened perlite or NAPA floor-dry, coarse sand ....)

Al

Would it be better to just wait til spring, or do you think it would be better to take the tip off now?

I'd take the tip(s) off now - that way you get a head start on the new branching in the spring.

Al