Ah dear. Fight fight fight. You were going to tie his head around with bailing twine sweet. Totally different concept to what kevinshorses has explained, his method the horse CAN straighten it's neck. Tying with bailing twine forces the horse to have his neck pulled to the side. It will teach submission, but will not create a supple horse.
Anyone can bend a horses neck left and right and touch their foot. It's a standard pony club 'trick'. Yes it is good if you want them to give their jaw, but if you don't have their head around without them being 'round' and vertically flexed, it will be a fruitless exercise anyway.
As has been described again and again throughout the forum in detail and a number of times by posters on this thread, starting with the head has little to no effect on the rest of the horses body. You can pull his head to the left to 'bend' his neck, but his body will simply remain rigid and stiff. Bending the neck WILL NOT create a supple body. The only bend in the neck I ever use is a little flexion in lateral work, and in trot and canter I will lightly flex a few degrees to the left, a few degrees to the right so test the softness of the jaw and poll.
Suppleness/bend.. whatever you want to refer to it as, comes as a direct result of an engaged hind end under saddle. You also have horses who are naturally very flexible, but this is certainly not the case for your horse by the sounds of it.
You say he tracks up... I bet he's just running through your hands and you have near to no control of the exact speed, tempo>>>??? Tracking up does not always mean that the horse is truly forward and engaged. Does he move off the second you put a light leg aid on? If not, he is just running on through the aids. You have to be able to put your leg on and expect an immediate forward reaction, and touch your rein and expect an immediate slowing reaction.
You want to have him doing wide circles, spiralling in and out, and teach him leg yield, then turn on the forehand an shoulder in. These lateral exercises are fantastic for suppling and getting full body bend, not just a neck that is pinned around sideway having no effect on the body what so ever.
You said you wanted to do figure of 8's, serpentines and one rein stops. Well sorry to say by tying the neck absolutely, will NOT help you with this, he may bend his neck but the body will stay rigid and useless. The only way you will achieve this movements is by working on the hind end with transitions and such.
But again, you seem like the type who wants a quick fix and a pretty head on your horse. So by all means. Go tie his head. I wish you luck.