I am building a new nscale layout, and am considering a helix for staging, or maybe even a second level. I am wondering what many would consider the minimum radius and slope for a helix to join 2 levels perhaps 8"-12" apart. I don't mind if trains are between for a while....it will increase run time.

Will this support plan wind up warping later? 

I'm in a climate controlled basement. Temps do vary by 10 degrees or so summer to winter but humidity level is relatively constant. Plywood deck is 3/4 inch birch cabinet grade. I had to modify my support structure so I now have the upper deck here supported on the sides of 1x2 strips ripped from plywood. I needed the extra height for the deck, and I new with a 24 inch wide section that the upper deck needed some lateral support under it or it would sag.

I'm planning to use 1/4" thick Homasote roadbed on the mainline of my layout, and with track down at the base (tabletop) level for the sidings, yards, etc.  The roadbed I've used thus far is the Homabed product produced by California Roadbed Company.  I really like the product, but have decided not to order any more due to the incredibly bad communication skills of the owner.  So I'm going to try manufacturing my own using Craig Bisgeier's method.

I am about to start my layout that I have been dreaming about for 50 years!  I have built several modules in the past and helped with a couple of club layouts.  My question is about how to keep the track noise down so sound systems can be heard.  I saw an article in the January Model Railroader about using Dynamat (auto sound deadener) under cork road bed.  Has anyone tried this other than the author?  What would you suggest?  Homasote is not a commonly available product in the Denver area.

Thanks