I have to agree with Jim, that 1/4" seems a bit excessive. We find 1/8" typical in old hardwood frames and even less in softwood. The big problem I have seen is actual "splitting" of the timber through the peg hole.
One unmentioned issue in the discussion is scarf joint location. Remember that the moment increases with the length of post cut off. The forces you are resisting in a short repair are primarily compression and shear. As you move up the post bending comes into play.
Bolted scarf joints work much better than pegged (bet you never thought you would here ME say that!) when bending forces are significant. If a solid wood repair is needed, try "under-squinting" or "cogging" the abutments. Cogged abutments are shown on the post repairs at the Cuvilly workshop page on this website. An exagerated version of this joint is the face halved scarf with bladed abutments. A little harder to cut but better for pegging.
A good reference for scarf joints is the illustrated glossary in R.W.Brunskill's "timber Building in Brittain".
Good luck with you repairs and remember to support the frame well. Safe work is good work.
Rudy R. Christian
