im with mike b. my fire truck has the 5x7's and i have no issues with them. my 40 has the 4" round ones and i have no issues with them either. what i had to do on both was to add a reinforcing plate on the inside of cab where they mount to stiffen them up and tighten them tight and it works well. my dump had the west coaster and are good too. they all have 4" spots on them which eliminates running into the side of and enhances backing up.
