You're ticket #42 on the ScannerCast ToDo list
This isn't as easy as it first sounds. ScannerCast can't stop sending data packets to RR while a suppressed talk group is active, so it would have to send a block of silence. The challenge, really, is how to dynamically generate that block of silence during ScannerCast startup so the block reflects the correct parameters for your feed (like the throughput rate).
I'm not saying I won't do it, or that it's too hard. I think it's a good idea, in fact, and would make a nice addition to the program. I'm just saying it's not a matter of "Hey... I think I'll go throw in the code for Mike's request this afternoon" :-)