My target gun is an MX8 with an adjustable comb and a fully adjustable GraCoil buttplate with KickEez pad. I have the comb as low as I can get it, and it shoots 60/40 high, right where I like it. The whole buttstock was given to me by a friend. I wouldn't have put the GraCoil on there myself but I have to admit, after using it for the last 10-12 years, it's nice having all the adjustments it provides. I haven't moved them since I put it on and got it set for me, but it sure made dialing it in easy initially.
Good catch on the OP's mention about adjusting the comb the wrong way. I overlooked that when I first read it.
SRH