I grew butternut (Waltham) and Zuchetta Tromba d'Albenga in 20 gallon Smart Pots this year (two vines per pot). I planted the butternut too late (early July) to get a good read on its performance, but it did manage to produce two small squash. I planted the zuchetta much earlier (May), and it really impressed me with its production and vigor. While not technically a winter squash, it's closely related to butternut (both are C. moschata) and, so, I'd I'm inclined to say that butternut should do much better if planted earlier in the season.

Shazaam, thanks for the input. How did you end up deciding on using a 20 gallon pot? That's a lot of soil!

When I pulled my sweet meat squash this year, I noticed that the root system was not very extensive or spread out. In fact, it was mostly a long taproot that went into the ground about 8-12 inches. So, I was considering using a smaller container: something like 5 or 10 gallons, but deep enough to accommodate the taproot.

I had both 10 and 20 gallon fabric pots on hand, and I chose the 20 gallon size since squash vines are aggressive growers that require a lot of water. Fabric pots dry out faster than plastic, of course, and I also used a coarse potting mix (Al's 5-1-1) that's not as moisture retentive as the typical bagged mix.

Excellent! Thanks much for the input and sharing your experience.