First as svHyLyte says I would also suggest getting professional advice if considering modifying the existing. Like all things, a mid sheeted boom is fine as long as designed for the loads under the conditions the boat is likely to be sailed in. I know of some new production boats that when imported for delivery
get reboomed down here because booms not up to the heavy sailing condition we encounter - so sailing intentions have to be considered.
As far as location of the mainsheet/traveller is concerned it becomes a personal thing. But some things to consider.
If sheeted at the end of the boom you end up with a lot more of the ropey stuff to pull in when sheeting compared to mid boom with few parts
and a powerful enough winch
. Some modern boats get around this by having a single
line as a sheet going from the end of the boom to the traveller (or often just a centrally located block if the boat is set up for vang sheeting) to a winch.
One needs to consider how often one is at the wheel
or elsewhere in the boat. On cruising boats undertaking passages (coastal or ocean) the usual by far is that there is no one at the wheel
most of the time. Mid boom sheeting with a winch by the companionway
may then be more convenient and drier if seas rough or raining and one has a dodger
. However, one can often also set this up, if wanted on occasion, so the sheet is also by the helm at times by taking one turn around the winch adjacent to the companionway
to give a fair lead and then taking the free end of the sheet back to the secondary winches which are often located beside the helm.
If just generally day sailing
around the bay for the fun of sailing and wanting to steer and adjust all the ropey bits all the time, then it may be handier and more fun to have sheeting and the traveller at the helm.
Many modern boats the boom does not extend behind the helm much or at all - which means in an in cockpit
traveller if end of boom sheeting is wanted.
Depending on your boat if you become overpowered in gusts the usual practice would be to drop the traveller first, not release the sheet, so access to the traveller can be handy. But not so important if one is cruising conservatively or if not and one has a fully battened main one can sail like a dinghy
and pinch up to depower the sail in gusts.
All just my opinion