I'll measure my spreaders next time. Length and 'deflection' ie put a bit of elastic between the shrouds where they pass through the spreaders and measure from the mid point to the middle of the mast. I got my particular ones with my previous mast which was the very first specific 'X' one for '654'. I transferred them onto '720's stick when I moved on simply to keep as much of the set-up the same as possible. (one less variable to consider) I'm not sure we really need spreaders with the M7 anyway - its fairly stiff and we don't put classical 'pre-bend' into it with high static rig tension. They might just prevent the mast bowing to windward at the spreader point under load as the top drops off a bit but that's just theory. I'll set one up without spreaders sometime and see what happens (I'm not recommending this as it might just break by the way) and I'm certainly retaining the lowers .... maybe not try anything in the Sheppey race though. As most know I'm not convinced (yet) that you really need an adjustable forestay with a good kicker/cunningham, a floppy rig and the right mainsheet tensions applied. It just introduces another raft of variables to try and get right all round the course. Pointing the sharpish end the right way just 1% more of the time will always give better much results still.
Time on the water is the most important thing of all - but it takes lots and lots of it .... The Blaze is deceptive being relatively easy to sail but there is a longish apprenticeship to get the most out of it (So persevere !) I also find just a few weeks away from it really takes the edge off even if I'm still sailing albeit in other classes The Blaze rig works best set up to be 'sloppy' it seems - therefore the spreaders work in a different manner to those found on 'tight' rig tension boats. The M7 'hangs' off the windward shroud and the spreader merely inhibits it inverting to windward towards the supporting shroud. From memory my own are shorter than most at about 26 or 26cm and are relatively 'forward'. This allows the boom out further offwind and when coupled with the sloppy rig - you can run deeper .....