Re: best weight placement
We recently got a couple 440 lb launch pads, 15" x 15" x 50". Type "440 launch pad" into google and you'll see what they are. Usually $100 each or so.
They'd work perfect in a boat layout like yours (the two boats we use are setup similar). We've learned on two separate I/O's that adding significant weight to the front/center of the boat helps make for a much nicer wake than adding much to the rear. Also makes it much easier for the driver to keep the boat at a steady speed.
Often we'll place one on the floor of the bow (it hangs a little over the ski locker door when filled, but we can still get access with a little muscle lifting that end of the bag) and fill it full. Usually that's enough and we ride.
Occasionally we'll toss the second one on top of it, and fill it about halfway, so we have closer to 650 or 700 lbs up there. Then with 3 people all staying behind the windshield and a 4th riding, the 3 serve as easily movable ballasts for the rear of the boat. Just be aware that we're bumping and likely somewhat exceeding USCG capacity plate on our boat when we do this. If we only have two people on board while 3rd rides, sometimes the second sac needs to come to the rear of the boat and set lengthwise across the floor of the rear bench, and filled maybe halfway.
If we have more people. we fill the bags with less water. People are the BEST ballasts...easy to move when they're in the way, self pumping, etc...but 3 or 4 isn't enough which is where these bags fill in.
But however you do it, a full 440 lbs up on the bow floor seemes to be the real baseline for our 18 to20 foot I/Os to drastically improve the wakes, then we tweak from there.
All hull designs and weight distributions are different and will react differently. You'll just need to experiment. I'd just recommend you get something of significant size...those 85 lb block bags look attractive because they fit into nooks and crannies, but you'd need like 8 of them all over the place to start making a difference, which is a filling/draining nightmare with only one pump. So just get a nice big one (or two), and if it turns out it's too big, just don't fill it all the way. But at least you'll have the capacity with ONE simple purchase and one drain/fill process, rather than finding you didn't buy enough of the little bags.
