A hook is a clubface issue...it is caused by a clubface arriving to impact closed to the forward swing path of the clubhead. While "lighter" trail hand grip pressure may make it easier for you to sense delivering the clubface more squarely to the ball through impact, it is not necessarily the root cause of your issue. Causes to clubface issues through impact usually repair themselves when intent is focused primarily on clubface orientation through impact. My suggestion is for you to spend a practice session hitting intentional hooks and slices focusing purely on delivering the clubface to the ball intentionally closed (hook) and open (slice) through impact. The sensations you glean from such a practice session will clarify whether grip pressure plays any role in creating the intended flight. You may find, as you assert, that a tight left hand will make it easy to slice and a tight right hand will make it easy to hook, but then again, you may discover grip pressure plays no role whatsoever. Whatever you discover, make a note of it so you can use the sensation the next time you wish to shape a shot on the course.

Nice work Trader57! The key to your success is that you "experimented". Too often golfers are looking for perfect results from Fundamentals. Fundamentals are a starting place. From there, each individual must do as Moe recommended..."find a blueprint for your own swing". Keep notes on what works and what doesn't and keep those notes that work in your bag to review before you play. Keep us informed of your success!