I think Mike (L) has covered it well
Personally, I think stability is the first thing. I've been in some right nasty boats on waters all across the UK and in many cases wouldn't care to repeat the experience no matter how good the fishing might be
However the ideal loch style boat has to drift 'nicely' downwind without assistance of a drogue to 'set' the drift. If you've got that as a starting point then by and large everything falls nicely into place from there.
Construction is largely immaterial to me if it will drift nicely, but the costs of maintaining clinker boats is a wee bit scary
The best drifting boat I've owned, and I maintain the best all round boat I've ever owned, was a Bonwitco 'With 475'. I went through a few boats, got my 1st one at 12 years old and bought/sold half a dozen before settling on the Bonwitco, bought it in 1988 and it was just turning 20yrs old then. Loosely based on a Skandinavian design it did everything well. Nice and beamy too. The design has been tweaked but essentially the same design is still in production today.
The next best I've owned was a 14' Norwegian bulit clinker 'Rana' which was just bloody great in all conditions but a wee bit tight in the beam and overall a wee bit small for a big loch in big conditions - common enough on Loch Shiel. Great single handed boat though. Someone made me a silly offer for that boat when they saw it re-fitted and about to be launched for a new season so it went to a good home in North Uist. I wonder if it's still on the go today
Mind you, even if it were, I'd still have the Bonwitco
I guess, to an extent, you have to start with the water and make the boat 'fit'. The ex-Leven boats are belters, I can recall being out on Leven in really rough weather and the boat took it in its stride. That's what you want at the end of the day
I'm looking into buying something for Loch Ness - perhaps - for the coming year, so all this stuff is very much at the front of my mind at the moment
H
PS - thinking about it..... being able to sit
comfortably is a real boon