[seL4] Get/Set multiple message registers with the one syscall?

I'm looking at `seL4_GetMR()` and `seL4_SetMR()`, which requires a syscall for each get/set. To my naive eye, it seems like you're much better off running `seL4_GetIPCBuffer()->msg` then reading/writing to each index as needed, turning multiple syscalls (one for each get/set) into just the one.

Am I missing anything? I was planning on replacing my Get/Set calls with direct array writes, but I'm wondering if I've missed reasons why I shouldn't.

Thanks, Ben