"As far as the surface cleaner goes, you will need a sturdy inner shell to create the vacuum and a brush skirt that will seal to the ground, with the vertical of the bristles being the only points where air comes in. Depending on the underside design of the rotoblaster, you may need to shorten the arms to allow the extra shell. The addition of 2 vacuum ports on the outer shell, should not interfere with the inner shell, and should th project go south, you will have an abused surface cleaner that may not work anymore."
Alan, what material is your inner/outer shell? We have 1"-2" of arm clearance. Thanks, Shane