The normal glass taping looks like this. Just around the ends to prevent splitting from the holed drilled to take the end lashings to the sails.
http://homepage.mac.com/peterhyndman.../spars016.jpeg
Also at the partner to prevent the pressure bruising or denting the mast.
You could glue in the knot and put a couple of layers of glass tape ALONG that part of the spar - maybe one about 150mm (6") long and one over the top about 250mm (10") long. By along - I mean parallel with the long axis of the spar.
The different lengths are to reduce the lump by keeping the two ends away from each other.
If it breaks, it breaks - but this would be good insurance. I would try to break the problem area a couple of days after the glass tape is applied, just to make sure no serious weakness.
Best wishes
Michael