Don-
Last year I took my mast down on my E-29 to address several issues. Among other issues, electrical needed to be replaced, and I wanted halyards run internally. Mast slap was a problem from loose internal electrical wire and also from external halyards, and I wanted an effective solution.
The electrical was pretty straightforward - 1.5" Conduit was riveted at 2' intervals all the way up mast (less a foot from the top and bottom), with an opening at spreader level and steaming light level for respective lights. There is technique to hold the conduit in place while it is being riveted I'd be happy to explain in more detail if you like.
The halyards were a bit more complex, and maybe someone will shoot holes in this strategy, but so far it worked well for me:
There are four sheaves at the top of my mast (two fore and two aft, with two sheaves in-line from a port/starboard perspective offering a fair lead fore–aft for two external halyards - Jib and Main). To internalize and effectively create management for four halyards, I drilled 5/8 holes in the masthead in-line with the inside of each sheave (holes had to drilled first through the masthead sheave cover, then through the plate underneath the sheaves welded to the top of mast column). Since my mast is 36', I thought there would be enough play in halyards even when pulled tight to generate a slap, so I rigged a harness at spreader level to restrict the oscillation of halyards as they vibrated (an 18' wavelength has less amplitude - ie. slap - than a 36' wavelength given the same energy). My harness was designed as this - I welded a plate (about 4"W x 3"H) to the bottom of the compression tube between the spreader tangs, and fastened to this plate (using #10's with hi-strength thread lock), four standard deck fairleads (two fore and two aft on the plate - directly opposite each other). Halyards ran from masthead sheaves thru holes drilled in plate atop mast column, thru this harness, and finally thru exit plates just below boom level. There are a few more details that are important to understand if you will undertake this project, but this is essentially it. I have no slap, nor any chaffing on the halyards. Only risk is the harness coming apart, but good welding and good threadlock should prevent this.
Let me know if you're interested in further explanation.
Best of luck.
