I use the Trucker's Atlas to double check Good Sam Trip Planner (I don't find dragging and dropping the waypoints to be a big concern) which I can then download to my Rand McNally 7710.
On this Summer's trip from Florida to Nova Scotia and return via Montreal I had only two Trip Planner warnings. A low clearance at Port Jervis, NY, and a propane warning on one of the bridges at Quebec City.
I e-mailed the City Engineer at Port Jervis and they went out and actually measured the clearance (I was OK) and also recommended a two block detour if I didn't want to chance it. I had my answer in 24 hours.
The propane limit was no more than two cylinders; so it didn't apply.
(There would have been another low clearance on US-9W South of Albany, but I knew about that one and told GSTP to avoid the segment.)