Use a waterbox... It's gawd awful without one and I noticed a decrease in low-mid power on my 750 without it. The waterbox principle is similar in most ski's but you'd have to physically make it fit in the hull and connect the hoses which is the reason you don't see a lot of inter-ski waterbox swapping.
Some people have taken out one of the baffles but honestly, it'd be more trouble than it's worth. You can get a RN waterbox which is metal for under $100, SN waterboxes for under $50, and you can buy new Factory Pipe waterboxes for $175-$200 depending on what you get.