So I love my Spike Solo+ 15g equipment. That being said, I want to share my experience. I made good beers with my Solo basket. Never had any issues outside of the initial batch or two getting my process down. That being said, I did ultimately end up buying an all stainless custom mesh basked from ArborFab. By efficiencies are way higher with the steel mesh than the spike basket and I have to do less babysitting of the mash and have less if not zero anxiety that I may have a stuck mash and scorch my element. Again, I had no problems making good beer with my Solo basket, I just couldn't get past the low efficiency numbers and didn't like the possibility of scorching my element. Just wanted to throw that out there because a custom mesh basket is probably half the price of the Spike basket and you get better efficiencies. Happy to answer any questions you may have and I discuss it a little more in this thread:
Spike Solo Owner's Thread
Edit 1: Also, a 5 gallon batch in a 20 gallon kettle likely won't work with the basket, I believe Spike has the minimum and max batch sized listed on the Solo pages due to the deadspace caused by the basket. I'll try and find it and link it here.
Edit 2: I was mistaken, Spike says in their equipment that 5g is the smallest size for 20g kettles.