Neck reining to 'On the bit' - what a journey!
I know this is heresy but a lady called Theresa Sandin gives some impeccable advice on all matters relating to neo-classical or traditional English riding on a web site named www.sustainable dressage.net. It is all written in easy to understand language. Go to the site and look up 'on the bit'.
Your planned journey involves changing the way your horse carries you, the way you sit on your horse, the way you hold the reins and the tack you use.
My own contribution - well - adopt the position of a quadruped.
get down on your knees and hands; lift your head up and put you chin at around 10.oclock Ask your partner to place upon the middle of your back a 2 year old toddler and then move forwards on your hands and knees.
A couple of minutes later do it again only this time:
get down on your knees and hands; point you chin down to the floor, lift your back so that your spine is curved -sit the toddler on the curved centre of your back and then move forwards on your hands and knees.
You'll discover that the power to move forwards comes from your hind quarters, but to move either of your hind knees, first you have to lift the front half of your body and one of your hands to do so. You don't pull yourself along, you push yourself along.
And just as importantly you'll find that you can take the weight of the toddler better when your spine is curved upwards as when 'on the bit' as against downwards when the horse carries its nose in the air.
A well schooled horse will carry itself 'on the bit' without any restraining straps and I suspect even when tacked up with a hackamore. The trained horse will hold the 'ramener' (snout to the floor,forehead perpendicular) head position with the lightest of pressure on the bit.
In your quest you are seeking to change the way in which your horse is carrying you - but in turn you must also be trained to help the horse in its task.
PS My horse DiDi is fully trained to go 'on the bit'
I watched recently a young girl ride my horse around the arena with the horse in a beautiful rounded posture - perfectly on the bit.
I personally can just about get DiDi to to go the bit at the walk and trot but I use too much pressure on the bit. Fundamentally my seat is wrong.
My wife can't get my horse to go 'on the bit' at all - but she is now trying to learn how.
Both she and I have been riding for 35 years - the trouble is, we were taught,
From the very beginning to sit a horse in the wrong way. Now it is said that we should unlearn the way we now sit incorrectly and relearn the correct way to sit - which isn't easy. The horse is ridden in the mildest of curved bar Myler bits and is never ever lunged in side reins.
Have fun in your journey.