They're not worth the pain. Once you thrown out your back while trying to horse around a 36-40" round, around to get it into a splitter you'll lose your affinity for it. Not to mention the horrible work height. I'm actually going out today to retrieve some Red Oak from a friend's ranch that's 34-38" through the trunk. I will quarter them with either my 372 or 9010 and then they become MUCH more manageable. My Speeco is a vert/hyd splitter, but it's almost never used vertical anymore. It's just too hard on the back. The other thing you could do (a bit of $$$) would be to mount a small, swiveling gantry/cherry picker on the back of your truck. You could easily pick up big rounds and load them on a splitter that way.
I didn't mean to be negative Nancy, rather I thought I'd give you a different perspective and maybe save you some $$$ and heartache.