diameter of handle possibly - generally speaking the thicker the grip has the tendency to quieten the 'release' so maybe something to look at & trial - would guess it's a combination of 'newness & uncomfortable' & the underlying fear of leftfield shots not allowing the release of the right upper chest/shoulder through the motion so the right arm straightens more & with the right side not coming through into impact forcing the right hand to lose hold (VJ Singh)
could just be as simple as unfamiliarity of position &/or unfamiliarity of pressure, & pressure points in the trail hand (main firm but not overtight pressure keys are the base of the middle two fingers (if handle is a little ways too much 'up' in the palm the middle two fingers can't apply consistent pressure at the base of the fingers so good) plus the pad of the right thumb pressure against the the lead thumb, this also begs the question of exactly how the right thumb is placed on the handle ideal would be little left of center grip
grip pressure at set-up if too tight it's a ways impossible to keep real tight grip throughout - naturally though if too loose through it 'feeling uncomfortably new' that ain't going to work either
though probably what playing into the issue no doubt will be partly to do with the 'hook' familiarity - so the 'fear' of leftfield not allowing the handle of club to travel to the left probably linked to the right side chest shoulder not being 'allowed' to travel through impact freely (you see this with VJ Singh as now part of his action as he doesn't want to hit it left having had major trouble with hooks
as part of the 'new' swing path you trying to achieve, nearer neutral, less from the inside thing to remember the clubheads travel still has to travel little ways back inside the target line, so leftfield after the strike
in a more neutral swing path, the handle through impact has to be traveling little ways more 'inside' so getting nearer the lead thigh this then is responsible for the clubhead traveling 'out' more - so clubhead travels less from the inside & on a more neutral path as a direct result of the handle moving 'left' - something for a reasonable striker of the ball to look for as they are not in the majority of folks fearing the 'over the top' shaft move - so handle not kinda moving either 'straight through' impact or 'raising up' & moving out to rightfield - this pretty common with better ball strikers who have a pronounced lateral forwards hip slide with the right side/shoulder moving back & down so really exaggerating the secondary spine tilt into impact.
