RE: raking it back
Like alot of what is found on the Guy Cribb site, if you take things out of context (the same can be said for this site as well) you can come up with several different "interpretations".
If we are talking free ride and wave sails, with very high tack to foot angles, then Guy Cribb is right on. If you rake a free ride or wave sail back until the foot angle is parallel to the board, you will be killing alot of the power in the sail and getting the CE (Center of Effort) of the rig way back behind the fin. This will cause the board to head upwind, won't help with early planing, and it for sure will kill the power in the rig.
So, for this type of gear, and freeride sailing/wavesailing what Guy Cribb suggests is essentiallly correct.
If you change the context, to Free race and race sails (which many of us in lighter wind areas use all the time, then what Guy Cribb suggests is very much not the case.
Free Race and Race sails have a much fuller foot with a much lower tack to clew foot angle, and most are made to be brought down parallel to the deck.
If you have the correct components (i.e. mast base/mast base extension with a really low pulley setup ala Chinook's CL250) then you can rig your sail really low, and get the foot of the sail right down on the deck (effectively closing the gap completely) with the sail at it's designed rake angle. Everything balances at this rake angle and it's up to you to adjust your mast base (in the mast base slot) so you apply the mast foot pressure in the right place to get the CE of the rig to align/balance with the CLR of the fin at this rake angle.
Check out any current race photos (especially formula) and you will see that for going upwind the sailors will have the gap closed.
So, it depends on what "sailing discipline" you are talking about, and what "design type" rigs/sails you are talking about whether "closing the gap" gets you maximum performance, or results in a grossly "over raked" rig that kills it's power.
So, I will neither agree, nor disagree with Guy Cribb's assesment, but he tends to make strong "always the case" statements that many sailors misinterpret.
Windsurfing technique is far too dynamic for anyone to apply words like always and never.
So, is "closing the gap" an anachronous myth....?
NO!..... if you apply it to modern free race, slalom, and race gear.
YES!.... well MAYBE...if you apply it to modern free ride(smaller sails espcially) and wave sails.... but then it never really applied to these rigs even in the past as for this type of sailing a deep low foot normally results in the sailor "dragging" the foot or having the foot get slapped by a wave, so the sailmakers "fix" this potential problem by making the foot run at a much higher angle.
Hope this helps,