I have grown these several times, since all I can grow are
moschata squash, and they grew well, and stored very well - I had one store just over 2 seasons in the basement, just to see. However, I like butternuts better, because of the increased amount of flesh in them - these only have about 1" thick all around the 5-6" squash. However, many butternuts I have grown did
not store well - Polaris is my favorite, though it is a hybrid. I just dried my last 2 polaris butternuts from 2018; Seminole pumpkin stored that well, when I grew it.
I didn't get quite as many squash per plant with the SP, though the plants can get very long, and one time it grew up one of my trellises, and it got to over 30' long, just on that part, and it seemed to produce more that way. The weight of the squash didn't seem to bother it - the stems just got thicker! That was the last year I saved seeds - 2015. Amazingly, when I used these seeds this last year in an experiment, using GA-3, every seed germinated, in both the treated and untreated groups! The GA-3 treated germinated faster, but all eventually sprouted.
I like that idea of crossing butternut with SP!
Update - after posting this, and being out in my garden and looking at a new (to me) variety of squash I planted - South Anna Butternut - I remembered the description of it, when I ordered it - it's a stbilized cross between SP and Waltham Butternut! Time will tell...
https://www.southernexposure.com/produc ... er-squash/