RE: GO questions
The 56 cm Someweed will help with your early planing.
Also, when you are able to sail with a vertical race fin, what is the largest size vertical fin you have.
At your weight, a 66 cm should be optimum, but if you really want to get the GO 170 planing early, then a 70 cm fin is the best.
As far as footstrap position, with all of your larger fins and rigs you will need to get the footstraps fully back and out board.
You could do as Steve suggests and use more inboard and forward FS positions, but in my experience, you won't be able to get the full performance from your board as this will move your weight forward and inboard slightly and diminish your ability to hold down larger rigs and to control the larger fins you are using.
It's purely "leverage" here.
If you go with inboard FS, your feet and ankles don't have as much leverage to control the rail to rail (roll axis) trim of your board.
Fore and aft (pitch axis) trim would be affected by moving your footstraps more forward, but it's ususally better to control the pitch trim of your board with mast foot pressure positioning.
If you consider that when you get your boom high enough, your harness lines balanced and the correct length your entire body weight is "suspended" from the rig and your weight is really cantilevered out
to counter balance the combined forward and sideways pressures developed by the rig, then there should be virtually no "weight" on the rear of the board (at least no weight applied by your feet as the leverage is all wrong for you to be able to "push down").
So, getting your center of gravity back on the board. amd well outboard to get your weight off the board and and keep it on the rig with all the force applied at the mast foot to put your board at the correct pitch trim angle for best speed and control.
It the angle isn't right you can't plane well, but you can move the mast foot forward or back to "adjust" the pitch trim.
As far as the "discoloration" of your board that's probably due to something in the water where you sail (where do you sail??) and there are a couple of "strategies" for dealing with it.
Go to a Marine store and get some fiberglass boat hull cleaner.
This will normally remove a tiny amount of finish (it's slightly abrasive) but it contains a wax that will prevent future discoloration.
We've discussed using some mild acids on the forums here before so when they get the search engines working for threads from the older websites you might want to do a search.
Or you can use the finest grade "ScotchBrite" or one of the dishwashing sponge pads thats guaranteed not to hurt teflon or non-stick pans, and simply clean your board, then wax it with a good carnuba car or boat wax.
It will still discolor a little over time, but not as quickly as the wax will seal the paint on your board better and you can always clean it off and re wax.
Getting the discoloration out of the non-skid is impossible, but you have an EVA deck on your GO so that's probaly not a problem.
Also, remember, the discoloration is cosmetic only. The dirty look and yellowing won't slow your board down, but it will look kinda ugly.
Hope this helps,