Kevin,
When you run these sort of tests I find it works best if you pick a spot on the tape, say the 2 foot mark and put a pencil point there. This lets you see in front as well as behind where you are focusing.
You might want to look around for an old 90/4 just to throw in the pocket. I loved mine for the size (tube of M&Ms) and look.
B2 (;->