The foam is compressible so it's possible to simply fit the strap as normal into those back holes. The first time does require some pressure to get the strap, K9 plate and screw to reach the insert and grab. But once it grabs, it'll screw down and the foam will compress. Over time, this foam stays compressed after a while, so it's easier to fit the straps on next time.
To be honest, I don't use the K9 plates on the Kode 86, 94 or 103: these models use the thick pads that are compressible, so the strap doesn't twist too easily anyway: the thick EVA pad will form itself around the strap ends and hold it in place nicely.
Regarding screws: send your street address and phone number to Marina@star-board.com
. She can send you some spare screws, M7x32mm. Please quote this email too, for her reference.
Hope this helps,