Effy... you're a senior member and have been around here for a long time and I'm sure you've read many a posts that deal with this subject. You're sounding like a newbie!:E You are obviously aware that weighing your coach is a must, to determine the correct air pressure...guessing that 5 - 8 pounds won't make any difference is just that...a guess. Come on, you're giving us senior members a bad name.:W
Go to any big truck stop....Flying J, Pilot, T/A, Loves, ect... and they will have a scale that you can use for a nominal fee. Usually the local dump will have a scale (but won't provide you with written results) and will do it for free. Moving companies.....Mercury, Nationwide, Atlas, Allied.... will also have scales. For others just check your yellow pages or google for your town. It's not that difficult.