I just finished reading the section on backcountry near Lake Placid. Apparently there is a long trail that is either skinable or snowshoeable (is that a word) that spans across several towns with maintained downhill riding areas in between. If I remember correctly they mentioned that it is illegal to cut new trails so the exhisting trails are the only thing that it rideable. The glades may be too thick to ride. But, don't take my word for it.
Also, I destinctly remember them mentioning that trail maps should be available in the Lake Placid area. You really should pick up the book mentioned above.