So if you really want to double C. Horn in a C 26, try this on for size. In no particular order:
Remove forepeak berths and install stowage. See Peter Hancock Kylie story somewhere in C 26 land.
Install WT bulkhead a couple of feet aft of stem
Install inside (Small jib)stay from this intersection on deck up to about 2/3 up the spar.
Install runners to oppose this stay. Use Spectra 6 or 8 mm uncovered for runners.
Remove and/or replace the keyhole hatch and/or otherwise make the access into the boat watertight, with for instance a Lewmar hatch mounted as seen on Open 60’s or Mini Transat boats. Seriously watertight as in upside down with hatch under water. Any type of slide in and fall out wooden washboards are completly inadequate for this caper.
Install hard dodger
Fabricate and install hard plastic windows over the larger ports. Off set from the cabin surface by 3/8" or so.
Fabricate, or have aboard, suitable size materials for use when both windows get blown out washing down a 30 foot wave at 15 plus kts sideways.
SMH rudder idea is good. Keep anchors close to midships once off soundings. Make sure they will stay in place upside down.
Remove furling, use hanks. When it really gets tooting the windage from a furled sail is not to be believed. When laying to a sea anchor a clean (furler free) headstay will reduce the desire of the bow to want to blow off to leeward.
Beef up mast step/partners & chainplates. There is a nice story on this in the photo section.
Install 3-4 foot bowsprit so as to get much bigger light air and down wind sails so as to keep (average) speed up in 10-18 kts. of wind speed of which there is plenty when sailing the ocean.
Along the same lines replace mast section with plus 4 feet height and double spreader rig. This will increase the shroud angle (reducing compression on spar) where it intersects the spar by a couple of degrees at cap shrouds attachment point and by several degrees at the lower spreaders & lowers. It will also give you a bigger sail plan for use in conjunction with the bowsprit and the high averages concept.
Use external spinnaker halyard (s).
Get a ATN top climber or fabricate same and practice using it when testing the Sea anchor, see below.
Carry 2 x 13 foot carbon spin pole for use in poling out headsails.
Fabricate a splint system (with dedicated cordage)that will connect the two poles so you can jury rig a spar when you get to the bottom of teh wave noted above.
Change to Dyform wire (keep same diameter-Dyform is stronger and more stretch resistant for a given size., refer to Navtec catalogue for particulars) for standing rigging except for backstay, see next.
Replace wire backstay with 6 or mm Spectra. Roughly 1/12th the weight. Make adjustable. The weight savings in this may well off set the additional weight of the spar height (maybe can use a smaller section). Need to review with spar builders.
Mount Monitor vane
Remove engine and related stuff & replace vacant space with stores
Buy Parachute sea anchor and practice using it, in anger, say 100 miles west of the Faralon’s in Feb in a real “black bowling ball low” from Alaska. BBBL so named by my SFO mates for the black spot they create on wx faxes.
Have two separate types of fuel sources for cooking. E.g. White gas/Kero camping stove as well as say a Force 5 propane gimbaled cooker.
Do not forget MRE’s. Not high cuisine but when you are cold, tired, scared and the boat is bouncing they taste just fine. I have crossed the Atlantic on a 30 footer with same.
Install good strong bookshelves and fill with favorite books. 7500 miles at 100 per day is 2.5 months....
Calculate proposed distance to sail (is it 7500 miles?)and figure on 2 lbs. of food per person per day.
Bring several 3-5 gallon water jugs and at least two funnels with some clear plastic hose. Use same to catch rain water. Do not drink the first takings from the furled mainsail: It is too salty. Let it rain for a few minutes first.
Leave fancy electronics at home.
Read list of books elsewhere in this site re ocean passages made before we all started dreaming of it. Hiscock, Smeeton, Barton, Lewis, Guzzwell, etc. Also an account by the Cape Horn Wind vane guy on the Alberg 30 site. He has done it already
Do not plan on getting rescued if the fertilizer hits you and not the fan.