OOOOPps .... and sorry if I am giving a wrong pointer here but in my book .........Leader and hook length / snood ......can be different.
On the end of 30lb braid I pop a 2 or 3 rod length of 30lb mono "leader"......this acts as a shock absorber for the braid [ braid has near zero stretch ] ..... Has a lead slider on it and a snap link tied to the end for attaching the hook link or snood.
The mono leader is also more abrasion resistant so is better on the sea bed....
When fishing for the more toothy specimens or over "rough" , steel strewn ground ....either a 70lb [ or whatever ] "snood " will be attached to the leader at the hook end to cope with the abrasion and, if deemed necessary, a wire tip to avoid a bite off.
As to backing ....using mono I would always strive to use at least a few more pounds breaking strain than the braid .... joining knot is going to be the weak point in the mono generally.
I don't know if it is every bodies idea of shangri la but it does for me with my range of species fishing !!
Charlie might "up" his leader material when fishing for conger because the steel wrecks are tough on the terminal tackle .... and more abrasion resistance is needed.
Wreck fishing for pollack and cod might also require heavier mono leaders but it is really "horses for courses". Leaders and hook lengths can be changed quite readily if conditions require it.
Happy to be corrected.... !! .....if I got it wrong that is !!
Dave