I don't know of anyone who would presume to use a capped 1/2 inch long ferrule.
Predator does and they don't presume to use them, they actually do use them.
All Predator ferrules are capped and the cap is quite thick. Depending on the ferrule model, up to 1/4" thick.
To Mr. Phelps,
Don't underestimate Ivorine3. It's more than adequate for the task.
Actually, even LBM is suitable for a J/B ferrule.
But if you want harder than Ivorine3, consider Ivorine4. Unbelievably hard and you'll need some very sharp carbide tooling to cut it.
Having said all that, IMHO, rolled & molded phenolic rod is about the best mtrl for this application and unless you're playing in a BCA league, you can make the tip & ferrule as one piece.
Jump handle length has been changing as of late. The trend is to a longer handle.
BCA equipment specs state that a cue must be at least 40" in length.
A 29" shaft & a 12" jump handle/forearm is 41". This configuration is legal.
However, greater accuracy and control are attained from an over-hand stroke as opposed to the dart style stroke and most players will prefer a slightly longer cue for this than the 40" minimum. A couple extra inches ain't going to hurt you.
Let the ribaldry commence.