Funny... I was playing with my setup today as well. Got a 5/8 2M/440 Larsen antenna mounted up the other day just clamped to the passenger grab bar on my bike and am seeing ~1.4 on an SWR meter. Not bad for a mobile, I think. I just picked up an adapter I needed this afternoon to finally get it all connected together. I haven't had much luck finding the extension cable for the SENA headset. Found one made for a security camera that seemed like it would work but they wanted $95 for it. I ended up just moving my SR10 from under the seat to the handlebars. The setup isn't as secure, and I now have a lot of wires on the handlebars, but what are you going to do? When I did so, I did notice that when I tried to exclude the Ground Loop Isolator from the Montana > SR10 connection I was getting feedback with the SR10 wired, so I wired the isolator back in, because I like the fact the SR10 turns on/off with the bike. (I used this Ground Loop Isolator, btw...). I didn't try transmitting because I was in the garage with a T-storm going on, but I'll try tomorrow. One thing that's not in the loop yet is I don't have a power connection to the radio (Kenwood TH-D72A HT, btw), so I'm just running that off it's own battery for now. But, I'm hoping the 'filtered' cigarette lighter adapter won't cause the same ground loop issues I was seeing with the Montana.