Is 1mm too tight a clearance between the chain stay and the crank arm?

Ben, the link in your OP tells you all you need to know. The left hand cup on the original TA BB is 1.5mm wider than the right. If you use a symmetrical BB then you need 19mm of protruding axle on both sides.

Now I'm really confused... Surely that would mean 106mm BB? 68+19+19?
Here is an image of the clearance, bear in mind that it is an 3 arm TA crank so might flex a bit. OH an weight wise, 107.6kg dressed and improving a bit, down to 103.1kg in the noddy.