Looking at what I can see of the hull I'm pretty sure thats the hull that is the same as the Tige PRE series. Tige fitted their first generation TAPS (hydraulic trim plate) to this hull around 1996 and it does make the wake steeper/mellow depending on the setting. If it is 20' it will be pretty much the same as a Tige PRE2002 and there are owners of these on
www.tigeowners.com that maybe able to help you with ballast ???. I have Tige PRE2000 (20' without the rear locker) that we currently use that has 2 x 200 ltr sacks either side of the engine cover 80kgs under the back seat and 160kgs of the lead in the nose with 8 peps on board kicks out a really good wake with the plate all the way down as we need to add more weight to the nose.