Three of us at my Club have Twists and we all use the nylon bolts.. Even with violent manuevers, there hasn't been any issue in using the nylon bolt. Just use one with a large head to spread out the load over a large area... make it as large as you can get and still fit inside the mounting hole.

No reason why you can't use a metal bolt either... but I've never seen an issue with the nylon bolt.

Bob