A couple of months ago I was helping a friend of mine install a tub valve. I believe it was a Delta. The instructions said to install the valve from 7'' - 18'' from the faucet. It wasn't an issue as it was new construction. If this was a remodel in a one piece tub, like a Lasco, with the tub valve at say 42'' the spout could be no lower than 24'' down from the spout or about 9'' above the rim of the tub. What's the issue about the valve being no further than 18'' from the spout?