I'm trying to get my lifter preload set and it is either right on the outer max (.060) without shims or right at the minimum with the shims (.020). Is it better to have it at the high side or the low side?

 

With out the shims you are opening the valves more, this puts them nearer to the pistons, as long as you are not having a piston and valve hitting each other than you are okay, putting in the shims will cause the opposite, and you will have less lift on the valves, either way as long as it is in specs, and no parts hitting you are good to go.