How to do media setup on ZQ510 in Xamarin.iOS

I've got a ZQ510 printer that I'm starting to use for QR codes on labels. I've figured out how to print the QR code to the printer using ZPL, but I cannot figure out how to get the printer to correctly paper feed for the labels we're using.

We're using 50.8 x 50.8 labels using a black bar separator, but by default the printer does not seem to detect this and the paper feed is random.

I believe from the Zebra support docs that we're supposed to use the following commands to configure the printer

! U1 setvar "media.type" "label"

! U1 setvar "media.sense_mode"; "bar"

~jc^xa^jus^xz

but I can't see how this should be done in Xamarin iOS. I've tried combining them into a string and sending that but with no success.

Any suggestions?