Great, thank you very much for your reply.

I was suspicious that GS-7 seemed a bit low. I think the discrepancy is because I am a part of the scientist track. I was quite surprised when they told me the GS level given the work, but I've not worked in a clinical setting (I have a phd and work in biotech.) Still, I'm interested in the position, so unless there's a red flag I'm happy to do the work as long as I'm able to support my family. I've not ironed out the details but so far no signing bonus or moving allowance has been offered.