If your boots are from Mike's XS they're going to tear no matter what you do or what fuel you run; but OEM boots will also weaken when the heavy OEM carbs are unsupported by the air box. Boots from JBM Industries are much more robust; Don James designed them to hold the carbs solidly without other support, and they do just that. Another solution (no pics needed) is to drill a hole in the top plate that joins the carbs and run a simple L-bracket to a breather box screw. Make the holes in the bracket and carb bridge large enough to run the screw joining them through a short piece of rubber hose for damping, and use rubber washers top, bottom, and middle (covered by flat washers top and bottom) to complete the damping.