plenum spacers

Don't know how many of you have tuned with spacers but I decided to try and improve the bottom end in my set up so I went to a 1/2" 4 hole phenolic to stop some heat transfer from the intake to the carb and gain better distribution while increasing the base height. At least with my set up it worked pretty well, I gained 150 rpm at idle. I am running an Edelbrock dual plane on my 440. I know the single plane like the open type on the top end. Once I punch the hole in the hood I am going to try the 1" super sucker to see what that does. Anyone else doing any fine tuning with spacers?