You might want to check out Ketucky State Parks for some trail information. Also through the website of "Bikes and Moore", a bike shop in Hopkinsville may be able to direct you to some trails or to bike clubs in the area that could suggest some ideas. Check out bike shop web sites in Bowling Green, Elizabethtown and Louisville....there must be some infor on trails around Mammoth cave. I know my reply is long and drawn out, but it may be of help through some diffierent ideas and opinions. I hope it helps.
Roger