How many liters is your Speed Slider, and how wide is it?
I think there are several models of the Speed Slider (I could be wrong on this)
and the particular size will make quite a bit of difference.
As far as how sailor weight figures into all this, suffice to say that the more you
weigh, the more sail you can hold down (provided you get your harness lines
correctly balanced and can commit your entire upper body weight to the harness).
There is a limit to how many liters you need to support your sailor weight, but if I remember correctly your Speed Slider is probably in the 120-140 liter range, right?
How big is the weed fin we put on your Speed Slider.
I cannot tell you what size sails until I have the volume/width of your board, and the fin size.
Hope this helps,