Can I use a hh with the 4in1 if I just turn down the gain and prop to 0 ?
and has anyone tried this if so does it hold ?

I'm trying to get that very thing to work. I'm told it will work. I think I've fried my 4 in 1 as it only shows red after initialization. I'll definately post here if I get it worked out.

Yes, but you have to remove the rx and mount it on top of the stock 4in1 to get to the connectors that you need to hook the HH Gyro to. See Ch3 and Ch4 are on the under side of the rx. Ch4 is for the gyro.