Replying to New Setup Ideas

right now i have a 9ft tall tower that is huge, probably a 8x4ft platform on top. However i have about a 12ft ramp down, which == too sharp of transition and no speed. It was great during the winter when i could fill in it with snow, but now i need to change some things. It will be a lot easier for me to lower the platform than extend the ramp, much more stability also.

So what height should the platform be with a 12ft ramp down to get the right speed. I have two 12ft box's that i want to be able to do.

Also i want to set up one of the box's on the down and the other right after on the flat (so its an urban style flat down). I feel that would be an awesome summer thing to hit. anyone see that working out well, or would that also be too steep of a transition, even after i lower it?

thanks and +K for good advice