There are lots of ways to use PVC to hold TI's, either on trailers, on racks and even just on the floor of your garage.
I've been doing it for quite a long time now and it seems to be the best way to store a TI. Before getting our trailer we just stored our TI on the garage floor shoved in a corner, of course it's always in the way of something so you have to drag it around on the floor. I always remove the AMA's and just pile them on top of the hull so the boat takes up way less room. Without the AMA's it's also way easier to tip the boat up on it's side to shove the scupper cart in. I always walk the AMA's separately. By doing it that way, the TI is no more difficult to pull around on the scupper cart than our old Oasis was (we are pretty used to tandem kayaks anyway, which have always been our personal preference, so we are used to them being a little bigger and a little heavier (but still way easier and lighter than two complete Single Hobie sailing kayaks, and way less time to setup).
If you go to Home Depot that white PVC is really cheap. For just storing on the floor instead of making a big rack that you have to lift the boat up onto, what we did was just laid a couple ten ft pieces of 1 1/2" PVC on the floor, and place the boat on them. The pipes fit nicely into the grooves on 11 inch centers running the length of the boat. I just put the boat down and kick the pipes under the boat, once in place you can drag the boat around all you like around the garage on the pipes (who cares if the pipes get all scratched up on the floor (I think both 10 ft pipes cost under $10 bucks). Why lift the boat up to waist high, if your like me not much chance your ever gonna work on it (pretty much no need, nothin ever goes wrong).
When we car top I just stuff the pipes between the roof rack and the boat so it evens out the load. Your straps hold everything down anyway. Actually on our last trip I found some closet rods at home Depot that are 8 ft long, and they are already PVC coated, I just used them on a big vacation, they worked great (really strong):
Here is a pic of our POS cheap Harbor Freight trailer (got it at Harbor Freight on sale for $140 bucks ( lol)), with the PVC pipes on it. I stored the boat on there just like you see for the first yr or so with no ill effects. However I did put longer and a little larger diameter pipes on there with wooden broom handles shoved in the pipes a couple years ago. The boat lives in our super hot South Florida garage, with no issues.
Just sain, I'm not about to spend $500 bucks for cradles to fit on my $140 dollar trailer.
FE