Heās not clipped and has a āfullā coat, but not a hairy yak kind of coat. I had a metabolic panel run on him this fall bc I thought his cold intolerance might indicate PPID or something. His bloodwork all came back well within normal limits. I keep hay in front of him 24/7. Heās just old and lean and little and cold sensitive as best we can tell. Iām unwilling to over condition him as I think extra weight could lead to more serious problems. Cheaper in the long run to buy him more blankets. I ordered him a heavyweight 360 gram with same weight neck cover yesterday lol. I might try a BoT liner for him too as his main āsymptomā of being cold is moving slowly / stiffness. Poor little dude. In comparison my bigger, younger, fatter horse was toasty warm in the same weather conditions in just a medium and likely would have been fine in a slightly lighter blanket.
I think the liners are supposed to be warmer than a single blanket of the same total fill weight due to layers but also ideally the biggest layer goes on the bottom so 
The XLs are not cheap. I ordered my most recent ones on Black Friday during their 20% off. If I recall correctly, they might also go on sale at MLK day or Presidents Day. I think I recall Stateline Tack having the best price during that end of winter type sale.
ETA: the little ponyās cold intolerance: this fall we had a few days where it drizzled rain constantly but I didnāt put sheets on the horses because the LOW temperature was for real 69 F. Near 80 for high temp. Horses have free access to a big, dry run in that they both use. Went out to feed breakfast one morning dodging the rain in my shorts and t shirt and thereās the little pony shivering his tail off. I felt awful and I know being wet is cold feeling but Iāve never had one shivering in 70 degrees before regardless! Thatās when I ordered blood work for him.