340 wall thickness & deck height

Generally I try to balance value (return on investment) and expectation. There are times when something is needed to accomplish the goal and the money has to be spent. The only alternatives to spending are gambling the final results, or lowering expectations. There is no "middle ground" there.
Also times when spending money is not going to return any value. IMO - bore size is one of those areas.
It's my opinion that the .005" of local thickness one saves by going +.020 rather than +.030, when the sonic testing shows thick bores (that one cylinder is really good for a factory block BTW) provides no return on the investment of custom .020 over pistons. Go +.030, spend less, and get the result you want. That's my calculus anyway. Ultimately it's up to the builder and customer. They have the relationship here.