OK... think I got it!
I can get my head around main sheet angle vis boom position being better purchase and tension w/a traveler.
I (vaguely, soon to be better) understand main sail shaping , re; keeping the boom at a given (lower) position to point closer.
I like the idea and prospect of "Travelers let you point higher, reduce weather helm, heel less and - when the main / jib is balanced even steer the boat."
Absolutely clear now,thanks all
Here's what I'm considering doing;
The W-27 has a relatively short boom with the gear terminating center of the transom; and the main sheet gear crosses quite a portion of the stern of the cockpit when centered. I believe that when let out,the gear will cross even more. Even considering that the boom is quite high off the deck, the lines will cross from considerably lower, blocking movement and potentially causing (some) hazard to occupants??.
With the existing locations, there must be/will probably be huge amounts of line consumed in a down-wind run. Scaling the dwgs,there's close to 6 feet between blocks...times four runs of line plus handling end means no less than 30 feet or so. When the boom's out only to 85 degrees, it works out to over 75 feet! That's a lotta line needing to be hauled and possibly laying about the deck until it can be squared away!
Moving to a coach top system reduces that amount considerably. Centered boom position it's more like 17 fee and at the same 85 degrees, it's only 26', even considering having the bitter end running the length of the 'pit!
At somewhere around $2/ft. that's a bit of dollar difference. Not enuff to cover the expense of a traveler; nor moving the purchase; but.....
I understand that there are engineering problems/questions associated with this change; ie: less mech. advantage, possibility of boom not being strong enuff for the placement.. all TBD
Next option would be the use of a traveler across the transom. All the advantages of a traveler, without the tech problems related to moving the position. It *might* get the lines outta the way some and will keep ( or, actually extend) the sheet length; but there will be advantages "traveler-wise".
All that said.....
It's only promulgating an intellectual exercise and trying to shorten the learning curve until I actually get the boat inthe water and move it under sail!
Any input welcome