Glad to see you got it. Stay above invert plane of top hole and you'll be fine. You can also drill some vent hole in the plate to balance out hot spots.
View attachment 353448 View attachment 353449 What i've learned from modding mine was once i got it sealed up tight and had my plate in it wanted more air to move heat thru cc to exhaust. Trimmed ash pan which sits in front of bottom of air inlets and blocks acouple sq"'s from under grate flow. I also added upper air inlets to help push air thru with affecting coals (read Dave Omak's -postings on upper air inlets, thanks dave) and opened up my exhaust to 3.5". Check out post #311 in this thread. Example, 60*ambient @235* I can average +/-5hrs full basket w/minion plate. Lower air open 10-15%, upper air 25-50%. With the bigger exhaust I can easily bring temps up fast by closing upper inlets and have all air go to grate. Really works well.