Hi David

The traditional solution for when you don't have a long enough ridge is to place a post or some other support at the joint. You could use a truss to hold the two ridge pieces up, but it is a lot more work to make a truss than a post. Of course, posts in the middle of a room aren't always an acceptable solution.

If you do use a post to support the joint, a simple and strong approach is a corbeled butt joint, which is a variant of what Jay was mentioning in his post. Y-- place a samson block or corbel about 4' long on top of the post and underneath the ridge. Simply butt the ridge pieces to each other and secure with adequate fasteners.

Generally speaking, I would not splice a structural ridge in my own house, so I can't really recommend someone else to do that.

Also, like Jay, I suspect the ridge is quite undersized as a 4.5x10.

Another approach might be to skip the ridge altogether and tie the feet of each rafter pair together with a third pole. If done properly that would eliminate thrust on the walls. Now if the roof pitch is below 25 degrees or so, I would stick to the ridge idea since the thrust increases as the roof pitch gets shallower.

(insert the usual disclaimer about incomplete information and how I am not an engineer, and you shouldn't trust structural advice from internet strangers, etc)

Best of luck, sounds like an interesting project.