How many spacers I can put on a Shimano hollowtec 2 BB for a 68 mm BB shell My bottom bracket shell is 68 mm English thread. 

I put a 1 mm spacer on the drive side BB to move the chain rings further away from the frame, so to prevent the chain rub against the inside of the front derailleur cage when the chain is on the small front ring and largest rear cog. 

I have already adjusted the FD limit screws, there is no way the FD can go any further to the frame. 

Before I adding the spacer the rub is very obvious. After adding the spacer the rub is very minor but I want to eliminate it. 

Should I　add one more 1 mm spacer on the drive side? I already added another 1 mm spacer on the non-drive side because left crank will rub the kick stand without it. So I already put total of 2 mm spacers on the BB. 

Can I add one more on the drive side?
On M542 crank set and 68 mm BB shell, I use one spacer on the left, and 2 on the right.

I think that on 68 mm shells you always use all 3 spacers, and distribute them on the left/right side to get chain line you need.