Hey there, you.
. Always the biggest of treats to see one of our oldest and dearest users (and once-vols)! <3
You should have no troubles with deep manual sex and an IUD. After all, it's inside the uterus, not the vagina.
However, I'd just bear two things in mind:
1) Your strings. If your strings aren't cut super-short, your partners will just need to be careful not to accidentally grab or tug them. If they aren't short, and you want to make avoiding that a gimme, you can always ask your healthcare provider to just snip them shorter for you.
2) How it feels for you. Most people don't feel an IUD when it's in, including during sex. But you know the drill: you never know, and your mileage may vary. In the event it doesn't feel good for you to be fisting with your IUD, then obviously that'll be something you don't want to do for now.