the shaker I have I got used from a friend and he brought the gray mini shaker from dtfsuperstore when he sold them.
ok so if i'm understanding correctly. the sheet metal you used, plugging some of the holes at the top of the oven and the take roll guards solved your edge curing issue. because these bulbs should have been longer in my option.
as far as using the hvac tape on the holes. I think this one might be different with the holes. 2 rows are offest from element 1 and 3, 1 row directly above element 2 and the other 2 rows of holes are in the center of element 1/2 and 2/3