OP said his wife's spine (I assume; it was spelled spline) hurt.
My wife wasn't really comfortable on my Road King conversion, even with the Tall Boy pillow top.
We ordered a Day Long seat that was built to our particular size/weight specifications. The base price was $605 but we paid extra because we are just slightly (!) overweight.
Custom Motorcycle Seats and Touring Saddles - "Day-Long" Touring Saddles and Motorcycle Seats by Russell Cycle Products
MUCH more comfortable.