Re: swept back spreaders without backstays
My Santana 525 has a 4/5 fractinal rig with swept spreaders (seems to be 20-22 degrees), a wire backstay at the masthead and wire/rope running backs off handers at the headstay level. I use the running backs exclusively and forget the backstay is even there except in a big blow. I've never seen any evidence that my rig has been over-stressed (and I check my chainplates, standing rigging, etc. pretty often.) I'm considering doing almost exactly what you are. I want to short the jib to a 105 on a furler and make up the sail area in a fathead full batten main with two reefs. (I also want to glass in a retractable sprit and add a masthead A-Sail but that's down the road) Now...this is not a set and forget rig. You need to be more mindful of conditions and reef earlier not later too keep her on her feet. For those that think deleting the back stay was bad enough without adding more mainsail area...I saw a system on a boat once...with dual running backs (twin masthead and twin headstay heighth runners). the mast head and lower runners are connected by an upper "loop" of wire with a pulley which is attached to a 2:1 / 6:1 tackle in the stern quarters. It is supposed to both provide maisail flattening at the masthead AND keep the forestay taut with one control line. Switching runners back and forth is more line to pull each tack but I got used to it pretty quickly. I'm not going to turn this into a 9kt surfing machine but I think the changes will cause the boat to make speed more efficiently in light to mid-range air and, with sufficient mainsail shape control, make it much more tune-able to changing conditions.