I don't know anything about WB breeding lines so can't comment...... but, I like his jumping technique- very neat in front. I'm not 100% about his back end though. Maybe close behind, and his hocks look a bit out behind him?
I'd want him to go to a mare with a very good hind leg/ quarters. Which mare are you thinking of him for?
I know what you mean about his back end. Though this could be because he's just coming up 4 and not fully mature?
I like his dam line a lot but not sure about usig an unproven stallion. Would be for next year tho so perhaps I should keep an eye on what he throws from this year.