The theory is that dropping the jib creates extra seperation between the kite and mainsail and helps make the kite more efficent. Some teams do it and others dont bother and its not really conclusive which is better.
There is a lot of seperation between the kite and jib anyway and the wind is always well forward of the beam so I tend to think its not needed but sometimes it does seem to work, but without proper two boating its hard to know for sure.

I'm going to ignore all the above discussion and go back to your original question...

Many of the changes you are referring to have two effects 1. reduced windage 2.reduced weight whether these benefits are worth while is up to you.

A 150mm (6 inch) strop in the main sheet will save you 1.5m 5ft) of typically 8 or 10mm of braid and replace it with just 250mm (10 inches) of say 4mm vectran or dyneema. It will also lower the VCG of the mainsheet block. This is all happening at the back of the boat where you don't want excess weight.

Reducing the shroud diam. From 4-3mm will not only cut down the windage by 25% but will also cut down the weight by 57% on a component with a VCG of say 3m this could be important. Remember too that your boats VCG not only effects the likelihood of capsizing sideways but also whether or not you'll survive going down the mine.

thanks for the info.

what is VCG?
and what does "survive going down the mine" mean?

VCG= vertical center of gravity, lower is better.
Down the mine shaft = a nose dive, face plant, stuff, etc.

What, you don't speak Aussie?

VCG = vertical centre of gravity
"Going down the mine" is digging your bows in down wind. Surviving means this doesn't become a pitchpole.

At the risk of oversimplifying (or being patronising) any moving body can be considered to carry its momentum (momentum = mass x velocity and is what keeps a moving body in motion) at its centre of gravity. When you stuff the bows going down wind, this momentum is what causes you to capsize. If the centre of gravity is high the momentum will have a larger lever arm than had it been lower, so if the boat's total VCG is kept as low as possible you're less likely to cartwheel.

I can tell you with 100% accuracy that windage can and does create a huge problem when racing especially when it comes from a prawn and garlic eating crew who suffers from an acute windage problem (or flatulence if you will)– going to windward is like breathing in a sewer and the eyes continually water, blurring the vision

Thats a different type of "windage" and easly corrected.... man overboard drill!

Thanks to all!