Personally, I'd put the band another quarter inch or so longer so the top of the band is level with the bottom of the hook shank, but that's my own preference, it depends on the size of the bait. Don't forget though that some anglers have the hook through the band so the hook is at the side of the pellet.
You need to know the reasons for using a hair in order to tie one. Basically it's for bait presentation and to aid hooking
If the hair is too short the bait will sit too close to the hook forcing the hook to sit at an angle and it could prevent the hook getting a decent hold, especially if using hard baits.
Also, the hair is supposed to allow the bait to move a bit more naturally, independent of the hook weight, however I'm not that convinced that makes much difference unless you are fishing big hooks and long hairs.
The length of the hair is normally set so the bend of the hook just touches the bait. This will allow a bit of movement but also the bait won't affect the hook when striking or lifting into a bite.
The above is for mainly coarse fishing, the science behind hair rigs for Carp and Specimen fishing is a topic in itself that will lead to numerous differences of opinion
My experience with float methods pellet just touching bottom of bend.
Most bites on the drop as fish is swimming so you need quick contact.
To keep pellet in required place under hook, whip on more turns of knotless knot!
Ledger methods - a gap from bottom of hook to bait of between half the size to the size of pellets being used.
Fish on bottom stop / tilt/ take bait/ untilt / move. The longer gap gives allowance for the untilt stage resulting (or at least aiming) to hook fish in bottom lip.
I tie my method rigs with hair standing off half way down whippings, that combined with modern patterns such as QM 1 is deadly.
Silicon - a can of worms!!!
Dont seen the need for pellet waggler or method rigsdue to the way I tie, it serves no purpose.
It does serve a purpose on specimen rigs such as Terry Hearns claw rig?
I find if i want a shorter hair i have the hair coming off the back of the shank after a couple of whippings, then carry on whipping down the hook, gives the effect of the bait close to the back of the hook, i find get very good hook up rate with this, must be harder for fish to eject without getting pricked.