If putting your vac motors in parallel, weld a box to the bottom of your waste tank, connected to 1, 2 inch stand pipe and bolt the vac motors directly to the box. With 2 vac motors, you will have 4 inches going into the manifold but only 2 coming out into the standpipe. Will increase lift slightly and drop your amperage. Anytime you use hoses to connect your vac motors, you lose some performance.