SPD Float and Tendonitis issues

I noticed my right knee gets a flare up of tendenitis on occasion. I can adjust the float, but I am not sure what would be a safe margin to go by to keep my leg a little more 'straight' in a pedal stroke to prevent tendenitis. I HAD Time Atac pedals with basically non adjustable float and this is what caused original tendenitis. Now I run SPD. I also was running a Easton EA70 100mm stem with 10 degree rise. I have a Gary Fisher Tassajara-15.5" frame and I stand 5'7". I felt extended out and had a hard time riding with no hands. Sense, I am with a 90mm 40 degree rise stem and this puts me in a more upright position, with my Chris King headset, handling is a dream. I have noticed an improvement with tendonitis a much less issue with the stem change. My seat postion is this: With crank at 6pm position my knee bends a little bit. With my crank at 3pm position the end of my kneecap aligns with the axle of my pedal (slightly behind axle for climbing). Will less float and a more straight pedal stroke alignment ELIMINATE flare ups of tendenitis? I do not want to injure myself finding out so what can I do? Thanks everyone in advance.