Sheri, the coats I like best are Petrageous brand, Kodiak model: https://www.chewy.com/petrageous-kod...B&gclsrc=aw.ds
The way these are constructed, there is a wide band that goes between the front legs to cover the belly. Then two wide straps that velcro together on top of the coat on the dog's back. these are the only coats that aren't a pain in the neck for me to put on my long coated dogs without getting all their hair caught in the velcro. They are cordura nylon, so water resistant on the outside. Kodi's is older than Panda's, and his is MUCH puffier, with a lot of insulation and a smooth nylon interior that doesn't mat him at all. The ones they make now are not as puffy, but for a dog with a lot of coat, it still seems to be enough. It really keeps the wind off them, which seems to be the biggest thing. Panda's has a flannel lining, and I was a little worried about matting when I first got it. but it does seem to be OK.
I wish they were still as good as Kodi's old one, but I still like them better than anything else I've seen.
Both Kodi and Panda wear the small... it's a teeny bit short in the back for Kodi, and a teeny bit big for Panda. It would swim on Pixel, but I think Tucker is sort of between Kodi and Panda, isn't he? (Kodi is 11 1/2", 17 lbs, Panda is just over 10", and 13 1/2 lbs)