I've wrapped the ferrule on a rod and before I finish it I'm having second thoughts. I've wrapped to within an eighth of an inch of the end of the female ferrule. Is this sufficient to prevent splitting or should I do it over? Thanks for your help.

Most ferrules contain some amount of interior reinforcement, but it is a good idea to make this wrap, with a bit more tension than what you would use on guide wraps, to within a milimeter or so of the edge. That's about 1/16th inch. I am not sure you'd have any problem with your 1/8th inch, but I like mine a bit closer. You may find it easier to begin your wrap near the edge and wrap away, rather than towards the ferrule end.

One other little tidbit, all fishermen should check their multi-piece rods several times during the course of a day's fishing to make sure the tip has not slid out on the butt section any. Ferrules that are kept well seated rarely cause problems. Loose ferrules where the tip has slid out on the butt can and quite often do fail.

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That's an excellent Tip, Tom . Checking for loose ferrules can prevent headaches down the road.
Also, in talking to a reputable blank manufacturer there is something they check for in quality fitting at the ferrule. Something called ferrule knock, which basically is poor fitting or loose fitting that is totally undesireable when accepting or rejecting a blank for sale.

Understanding this, might also be a good idea as you begin you rodbuilding with a two piece blank. Tight fit is essential and also the
ferrule wrap adds the extra security and finish.

my 2 cents.

Rich
Richard's Rod & Reel