I now think slugs are the way to go for your First 235 sails.  The speed penalty is negligible due to the mast and the ease of use for single-handing is far superior.  There is also less wear and tear on a bolt rope.  One person can raise or lower the sail in 10 seconds.  One problem has always been the open gate on the Z190 mast.  You can opt for the Stopper Screw solution (see bottom) or go the ultimate with aluminum gates.  This allows the slugs to go down to the boom for better flaking and is the best solution.  Greg Follmer illustrates his handiwork below - This solution doesn't bring any binding and looks like a winner - kh     All pics below click to full.

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I have found this mast gate works very well and is relatively easy to make.  They are made of aluminum doorway threshold material. I was looking for a piece of aluminum with a cross section that would fit down within the notched area of the mast (where the feeder was removed). After checking several weather stripping extrusions, I settled on the following Frost King "Seam Binder" from either Home Depot or Lowe's (view product and description at Doityourself.com).

The material was cut in half lengthwise; the edges with the legs fit at the mast slot edges. After cutting, machining, filing, and sanding, I got the pieces to fit flush inside and out. The plates are held in place by screws inserted into tapped holes in the mast.

The slugs slide smoothly since there are no protrusions for them to catch on.

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Don't have the Gates made yet? 
The two easiest stopper solutions are below:


US Spars Sail Slide Stopper
Enter Part #4609 in the box to upper right
http://beneteau235.com/first_235_us_spars_order.htm

Davis Stopper Screw
http://www.davisnet.com/marine/products/list_marine.asp?grp=m22-3