There are a bunch of threads out there on Summer setups and drop in plans. I had an idea and instead of replying to all of them I'm just creating a new thread.
Using regular carpet for drop ins or landings.
Obviously the best setup would be one that you could use all year round. Someone was talking about covering their drop in with old carpet. That would probably work if you sprayed it down with a mix of water and bio degreaser. Bio degreaser is basically soap that doesn't kill your lawn.
There are a few brands that are sold in hardware stores or you could use biofriendly dish soap. If you build your drop in and cover it with carpet, then the snow will stay on it in the winter or at least you can spray a little water on it and it will be fast. The carpet would add a little weight to it, but it would still be pretty easy to move around. This would be a cheap, easy way to build a 4 seasons set up. The only thing you might want to do is spend a little more $$ on pressure treated lumber. Because having the carpet on it will keep the wood damp, it will probably rot quicker unless you seal it somehow or use wood that's more water proof.
If you had natural terrain, you could just roll out the carpet, spray on the water/bio degreaser mix and you're ready to go. You could just roll it back up when you were done. Anyway, I think that just about any carpet would work and you wouldn't have to spring for snowgel.
PVC
I did some research and it looks like you want to use white PVC pipe. From various plumbers blogs (pretty exciting stuff) they say that black PVC is made of ABS which is weaker than PVC. If you buy black pipe it could be the ABS stuff. They all said that this stuff shouldn't be used for burried plumbing because it's too flimsy. The black stuff will probably break easier, especially if you are using it in the winter. I am not saying it will break, but the black ABS pipe will break before the white pvc breaks. I heard about a setup that Bobby Brown had at his place. He screwed about 10 1 inch diameter pvc pipes to a 10 inch wide piece of plywood or a 2 x 10, from the bottom. It was like a 10 foot long funbox with pvc as the surface.
Slope
I haven't built one yet, but I measured the slope of the dropin at Woodward at Copper. It was a 40 degree slope. I think that the carpet /bio degreaser combo would be faster than snowflex the way they had it prepped. Something closer to 30 degrees would be about right. The height of your dropin would depend on the size of the ramp you built to get onto the the rail. I think to be safe I would go with a ratio of 6 to 1 so basically,if your jump was 1 foot high, your drop in would be 6 feet high. If you find that you aren't getting enough speed, try a different bio degreaser or go heavier with the stuff you have. I know if you get the combo right it will be as fast, if not faster than snow.
Ladder
I've seen some ladders that multiple hinge points. They're kind of pricey, but this could be the ultimate mobile set up.
http://www.gorillaladders.net/pc-15-5-17-fiberglass.aspx
You could just unfold it, throw a plywood plank covered with carpet on the inrun and one on platform if you wanted and you'd have an instant dropin. The other great thing about this is that it would be pretty much indestructible. Yeah this one is like $250, but I bet they have them at some of the discount tool stores for less. It would be worth it just to be able to set up anywhere, anytime in minutes without having to shovel. This would be ideal for Urban.
Sorry to throw another similar thread up, but I hope this helps and I didn't want to post the same thing in 5 different threads.