Any dealers that say "No Haggle" or want to show me the invoice price, are the ones I stay away from. Buying services such as Truecar.com are in bed with the dealers. With the advent of the internet, dealers started to manipulate the invoice price as well.
I have used
Fighting Chance with much success - went for a test drive and negatiated the price from emailed bids from several dealers. Go ahead and read the info posted in detail. I'm not affiliated with them - as a matter of fact, found the link for them on here.
As for RVs/TTs, your simply nuts if you pay MSRP.