To run internally you need to install an entrance and exit plate ( see Isomat Halyard exit plates
) in the mast, the first a foot or so below the mast head, the second 8 feet or so above the deck. Several years ago I installed a spinnaker crane and chose to run the halyard externally even though the mast has the spinnaker plates already in place. I consider the ability to jump the halyard worth living with some windage, a serious racer would run the halyard internally. Just remember to tie the halyard back from the mast when not being used, as all halyard/control lines should be ...slapping halyards are a sure sign of a clueless sailor.