We just took a trip to Texas, and used ours for the dirt bikes. One of them was HUGE. KTM 950, with the biggest tanks ever made for that bike.
We just bolted a 2X12 to the bottom of the lift when we were moving bikes in and out. Temporary, but I will be using something else eventually.
I know I have a picture here somewhere...
Here's the beast on it's way in for the first time. We all crossed our fingers. I should point out that the lift chain broke a day before, and we shoved screws in it to hold for the duration of the trip. It made it, somehow.
I also, was planning on making an extension that slides out, Would be pretty simple too. Doesn't have to be terribly wide, as you can see from what we used, we had no trouble at all with the narrow platform. You do have to make sure you get it on there though.