I just installed a Nashbar Trekking Crank onto my MTB (triple 110 mm BCD). After I got done I noticed that I only had about 1-1.3 mm of clearance between the tip of the inner chainring teeth and the chainstay. Although the chainstay approaches at an angle so that only the tip of the teeth come close. I also measured the front chain line at 45.5 mm and the rear chain line at 43.7 mm with a calipers using the method in Leonard Zinn's book. This chain line seems good to me. The BB is a 68 x 113 mm FSA Platinum Pro and the spec for the crank was to use a 113 BB with 1 1/8 inch tubing, which I have. Also, the clearance of the tip of the non-drive side crank is only 5 mm (10 mm on the drive side).
Assuming that there are no other problems here are the options that I am contemplating.
1. Run it as is. Hopefully 1 mm is enough.
2. I just read a method to adjust the FSA Platinum Pro BB. Apparently there is no lip so spacers can not be used but the entire BB can be shifted left or right. I could give up 1 mm on the non drive side but that would only leave me with 4 mm between the crank and the chainstay.
3. Get a larger BB. The spec for the crank says only to use a 113 or a 118 mm BB but I suppose I could get something like 116mm, which would give me an extra 1.5 mm on each side. This will however make my chain line worse but probably not terrible.