Shower/tub plumbing

I am installing a jetted tub in a three wall alcove with a shower surround. I would like to deck mount a spout in the front corner of the tub deck instead of on the wall and use a single handle wall mounted control valve to control the tub fill and shower.
I was reading somewhere about limiting the distance from the valve to the spout to 18" prevent what I think they called "water rise" causing water to come out the shower head when filling the tub. I have seen a Kohler valve that has the diverter mounted at the valve, but it has instructions not to use multiple elbows, or PEX between the valve and the spout.
Does anyone have suggestions or should I re-think my plan?
Bob

I would think that if you increased the size of the pipe immediately after leaving the valve assembly that you could alleviate this problem.

Most valves have 1/2 inch outlets so I would go immediately to a 3/4 inch pipe all the way to the remote spout. I don't know if "they" make a spout that uses a 3/4 inch connection but if you could find one it would be preferable to reducing back to 1/2 inch at the spout.

HOWEVER, I am not a plumber and I have never tried this...but I might.