With a 720nm filter, my experience is f16 at one sec for bright sun. I used that for the Efke, and just did my first roll of Rollei and got good negatives. IMHO, trying to use a light meter for IR will often be misleading. IR is not always proportional to the visible spectrum. I'd start at the f16 & one sec. and bracket for the first roll. That should get you started.