I've recently started barrel racing. My current horse( the bay with me on him) is doing well, he's very fast and tall ( not so good I've been told), but he's slow on turns. I have to work extremely hard to get his flexibility and quickness up and it deteriorates quickly if i spend a few days doing jumping or trail riding. ( Part of this is due to his long back) I do not know whether to continue with him. Do you think he's a hopeless case? He is the first pic. There are three horses I'm looking at for prospects, but again, I'm new to this. The first is a big( not necessarily tall) , grey-ish mare that has a lot of bulk as a yearling. She's fast and quick. The second is a sorrel gelding that has barrel racing and halter in his bloodlines and as a weanling ( now yearling the pics are of him as a weanling) has a lot of mass, so he's gonna be big. The third is a rather lean and somewhat muscular filly that will be steel grey. ( Colors clearly don't matter, but that way you know which is which) She seems to be the most barrel typical horse to my eyes. Which do you think is built better for the job? ( Any horse will have to be able to do more than barrels) Laso, a fourth. She's in an awkward yearling stage in the pics, put they said she's super fast and quick, but has an attitude. The above horses all have calm dispositions, with the exception of my current bay, who has an attitude.Also, does the long back inhibit turns? Does excessive muscling and bulk slow the horse down? Do larger horses struggle more? Thank you for the help, I greatly appreciate it!