Most any bag that style will fit there. Some are hard and round, this one is soft and flattens out some to fit in the frame/fork cavity. There's 3" of air space below it and the fender. I put two-piece velcro patches between the rear of the bag and the forks to prevent movement and scratching.
What's it good for? Looks, covers the ugly bottom to the triple-tree, carrying stuff that can afford to be stolen (I put my orange HD folding tool deal in there to keep it from blowing around), and blocking the updraft from that area that tends to hit chest high and blow dirt into the eyes. As noted, it's easy to remove when hot out and a cooling draft's wanted.
I had no cooling issues with the last bike install per the oil temp gauge on the dipstick.