you're on the right track. i get a great wave after having installed a malibu-style surf gate last year. do the platform and gate installs together and integrate them, that's what i'm going to do this spring as well. as far as weight goes, i run a 650lb diamond sack under the front seats, fits perfectly. with that and 800's on either side of the motor, you can make a great surf wave. you should upgrade your prop to handle the extra weight though. i went with an Acme 913, 10.5-pitch and it works great.
'88 Sunsport, 2250lbs ballast, automated surf system, home made surf exhaust, surf flap, ACME 913, Krypt 6.5 HLCD's, Perfect Pass Stargazer
2007 Centurion Typhoon to be upgraded this winter!