Thanks for all the input. DeHe, that is great news about the teacher this year.
I talked to one of the OTs yesterday about my other kid, DD, who has good handwriting when she tries, but she has complained about her fingers/wrist hurting. She presses down really hard. The OT suggested that I give her a mechanical pencil and see if she stops complaining about pain. If the pencil breaks when they press too hard, they learn to not press down so hard (as the theory goes). I asked her if DD should use a pencil grip, since she often holds her pencil the same way as her brother and I (with the pencil in the junction between her thumb and hand, not near the end of her thumb). The OT I talked to hesitated and didn't think it would be necessary for her to use a grip--main thing is getting her to not press down so hard. DS has an OT therapy appt. today (the OT I talked to about DD was a different one) so I will ask more about this, and whether it's really a great idea to push having a perfect grasp given how weak his hands are.
When I tried to use his Crossover grip my writing suddenly became very sloppy and difficult. So I can see what his issue is.
If someone has a recommendation for a grip that they found helpful for their kiddo with weak hands, let me know.