The only thing I'm wondering about is the need for 12oz's. That seems like allot. The Saito will handle it and on a 4* it will not make that big of a difference, but if he is able to remove half of that then if he thinks it floats now, 6oz's will make a difference.

I use an OS91 Surpass on mine and needed no weight at all by stuffing a 4 cell 2700mah Expert batt up under the tank that weighs in at roughly 6oz

Here are the engine weight's

Saito 100

Engine (Only) Weight: 19.5 oz
Muffler Weight: 1.4 oz

OS91 Surpass without the pump

Weight-With Muffler: 24.2oz

So all total I have roughly a 3.5 oz heavier engine in mine and probably a 2 oz difference in battery although I'm not sure of what battery he is using