Thank you Dave!
I have not moved the chain plates. The oday stays we’re short, thankfully, so I’ve added additional turnbuckles to upper shroud/forestay and some chain to lower shroud.
My SA/disp is 14.25. I understand <15 is underpowered and am ok with this. My chief concern is the difference in ratio of SA between fore and main between the two sail plans, leeward moment and potential for capsizing. I’m not going to use the jenny because of this.
I believe mast is designed for the load consistent with the size of the sails. I have removed the h26 tabernacle and replaced with the oday tabernacle, which required drilling new holes in the latter to match the tapped holes in the h26.
I have repositioned the spreaders to match the angle of the tabernacle/chainplates on the hull. It looks like I’m still forward a couple of degrees. I’m considering moving the spreaders further back still to correct this as it’s critical to the h26 design without a backstay.
there are mounting points on either side of the cockpit which appear to be reinforced to the same degree as the chainplates. If I want to be extra conservative with the standing rigging I could instead add two back stays, one on each side at these.