RE: board taking on water
I deleted my double post and your 2nd post as I think we can work with this issue in just one thread a little better.
OK, you are an entry level beginner type sailor, just getting your basic techniques mastered, correct?
There may be several different issues that are creating your "deck is awash" situation.
First, with rigs smaller than about 8.5 m2, I would suggest placing the mast foot behind the center of the mast slot and it would probably be even better with the mast foot very near the back of the slot.
Your GO board has a nearly flat planing surface back behind the front footstraps (in their farthest back and outboard positions).
Ahead of this "planing flat" is the "rocker transition" where the board's bottom shape (the rocker line) changes from nearly flat to a constantly increasing curvature up and away from a straight line extended forward from the planing surface at the back.
So, in order for you to "trim" your board for the optimum fore and aft (pitch axis here) angle of attack (AOA) you need to place your weight so that the rear planing flat of your board has a slight upward slant from the tail forward.
This means you need to move your weight back on the board in order for it to plane. You also need to move back for the rockerline to be at all efficient even when sub-planing.
So, my guess would be that by putting your mast base all the way forward, you are adding weight to the front of your board.
Having the weight this far forward is lowering the front of your board too much and allowing the water to flow over your deck in the area of the mast foot.
Moving the mast foot back, and the center of your mass as well will bring your board into a slightly nose high pitch attitude.
This will "incline" the planing surfaces at the back of your board slightly higher at the front and make it so your board can plane when you achieve enough speed for the planing surfaces at the back of the board to support your weight plus the weight of the rig.
So, in essence, you are placing your rig too far forward, and you are standing too far forward on the board.
Do you step back on the board and get both feet behind the mast foot BEFORE you rotate your shoulders to power up the sail?
Also, with your 6.6 m2 rig (what brand (s) and model (s) of sails do you have?) the additional weight of the rig, placed at the front of the mast slot, could be enough to sink the nose slightly.
If you get your weight behind the mast foot (front foot 4-6" behind the mast foot and about 4" upwind of centerline, back foot about your shoulder width behind the front foot with your back heel placed right on the centerline and the foot extending downwind of the centerline) your board will ride with the planing surface at the back either level, or with the front slightly higher than the back so your board will want to "climb over" the water.
Ultimately you will move back even further as your board develops some speed and can support your weight even further back.
It's basic physics that the planing surface needs to be "trimmed" with the front higher than the back. If your planing surface is lower at the front, the board simply cannot plane or even increase it's speed very much as you are "pushing" the water with the rockerline, rather than elevating the nose so the board can slide up over the water.
Putting your boom height up high, at your skill level, isn't going to help you plane.
You need to have the boom at about shoulder to chin level, where it's most comfortable.
Work on getting behind the mast, getting the water exiting from under your board back behind the mast foot, and then having the board accelerate as you move back.
Move back slowly, and progressively, at a rate that keeps your board constantly accelerating. If you move back too fast, the tail will drop, and you will be creating too much drag at the back of the board because you have too much pitch angle.
Give this a try, and let us know if it solves your "deck awash" issues.
You can post here on the Free Forum, or complete the registration and have a look at tons on information on trimming your board out correctly on the "Windsurfing School" forum.
Hope this helps,