A new mic as someone already pointed out in the stream chat seems quite necessary... or some tweaking on the audio.
Two minor issues I would like to point out: 1. Interrupting Sayle's speech every now and then; I realize it's hard with the delay and all but you should try and find a way to avoid doing that, it disturbs the flow of the cast.
2. Try articulating a longer train of thought every now and then. Sometimes it feels like Sayle is doing most of the casting (which is fine) and you just offer a word of approval every now and then (which might come out as a bit awkward). I don't think this is necessary because if you already do speak out, you usually make sense, so don't be afraid of doing it more often (while keeping point #1 in mind).
This is just my humble, uneducated opinion but hopefully you can make some use of it. Overall I definately enjoy the co-casts, keep up the great job!