I am in the process of designing my HO layout. My question is about acceptable grade on an elevation. I want to reach the highest elevation I can with a track length of approximately 40'. It seems depending on who you ask it is permissible to go as high as 4%. I can attain a max. height of almost 6" at a rate of 3.5%. I plan on running short trains on a NCE DCC system. Is this too much? I am confused because some companies sell ready made risers to 4% grade. Looking forward to some input on this.