Welcome Rune, sorry we've been slow to greet you.
If you look in the SH3 mods workshop forum, one of the (sticky?) threads is S-boot. This will give you the link to the download.
Enjoy the mod. I play it a lot, it's great fun.
brush up on manual targetting and spped calculations though as you have to guess the speed and when to launch. real point and shoot style!