There should be 100lbs or so in going from a plywood interior to aluminum. Will 100lbs even make a noticable difference to a 30' sonic?

Possibly 1 mph...

1. Since I have no way to weigh the hatch or seat base, nor do I know how much the aluminum weighs, I though I would ask figuring someone might have some info.

2. I'll ask the questions! :D

I gotta say ditch the speakers. Not only will you shead some weight but your bolsters will be more functional ;)

One thing to be careful of is where you remove the weight. The stern is ok but stay away from the bow....you need weight there. The aluminium is a good idea but be careful. That stuff will move a little and chaf. How to attach it is another worry, it needs to flex a little or it will start crazing the gel. These items will save weight, that is for sure, but will it save enough to make it worth it. I removed the entire cabin and made bench seats in my Donzi, I bet I lost 6-700 pounds. This gave me about 5 mph with new engines (stock rebuild) and gave me tons of room below. I would fill the tank based on what the seas were like. I would fill it when the waves were big for weight and keep it low when I wanted speed. At 200 gallons @ about 5lbs per gallon this is a good amount of weight. If you are going 90 now I would save up and gain HP, not loose weight.

Re: How to "lighten" the load?
 

How bout putting Pauly K on a diet? :D

Re: Re: How to "lighten" the load?
 

I thought about pouring ketchup on a few areas I want to shave some weight from. Once he crapped it out I'll be good to go!!:D

fill the cabin with helium!!!!!!!!!!

Is the bottom blueprinted? do you have the best props for the boat. If you have big power already get those two things done and let it eat. I wouldn't't make the boat not as nice to be on just for 1-3 mph.

I want to go 120 and still have a big cabin with stand up head, That is why I am going to sell a perfectly good 2000 42 Sonic that is turn key and never lets me down. For a OL that cost 2-3 times as much that will blow up sooner or later piss me off and make me mad. Sounds real smart, I can't figure me out.

Keep us posted on how the aluminum seats and deck go. I plan to do the same with my Magnum when the time comes.