A couple quick thoughts here,
I should note that I was unable to open the website and so was unable to actually see what the Barros 28 looks like. You asked whether you could address questions directly to Mr. Barros. As in most things this is a matter of Mr. Barros'' personality. Some people do not mind answering questions and will take time to answer you and others will not feel comfortable answering your inquiry. You should be able to write to Mr. Barros and ask him the kinds of questions that you have raised. That does not mean that he will answer you.
I am not sure that your questions about why the designer chose to do certain things are impertinant. But I am not sure that I would phrase them as you have. Designers are human and can be opinionated just like the rest of us. If you ask these questions in a neutral and non-acusatory way, you are likely to get the designers best explanation of his opinions rather than a defensive or agressive response.
From the discussion this sounds like the Barros 28 is an older style design, especially if it resembles a Cal 2-27. I would assume that is why it has a large
jib, small mainsail rather than a more traditional or more modern fractional
rig. (For the record, fractional
rigs predate masthead
rigs and have come back into vogue now that the race rules no longer over penalize them.) As far as relocating the traveler you would probably do best mounting it on the bridge deck where it is in easy reach of the tiller.
Multiple chine plywood is a reasonably good way to build a boat although it still requires all of the skills and care that other forms of composite or semi-composite construction would require.
The deal on a coach roof stepped mast is that you need to develop a moment connection between the jackpost and the base of the mast. In that manner you transmit no more side load into the house than you would with a keel stepped mast, and argueably less if designed properly. With either a keel stepped or deckstepped mast, there should be large knees or a bulkhead adjacent to the mast to distribute the side loads into the deck.
On a 28 or bigger footer you will want redundant
winches because there will be times when you want to adjust a halyard or reef while the the
winch in question is still in use. These only need to be single action
winches and so are pretty inexpensive. On the other hand you might do two speeds so that they can be used with your
spinnaker sheets.
You might also look at the Dudley Dix http://www.dixdesign.com/designs.htm designed smaller version of the Didi 26 and Didi 34. These are modern, well thought out smaller boats aimed at amateur construction. From what little opened on the Barros site, it appears that the Didi 34 is roughly the same displacement as the Barros 28 and so should be of similar costs to build and similar difficulty to sail.
Regards,
Jeff