Hi Alistair,
The total weight for the old 10", including optics is 11.85 kg, without optics it's 7.85 kg.
For the new 12.5" so far I've calculated the expected weight based on the exact volume and density of the different materials (birch plywood, aluminium, steel nuts & bolts). OTA alone excl. optics should be around 6 kg, and with optics ~11 kg.
I'll be using a conical mirror which will save quite a bit of weight. The weight of the conical 12.5" primary is pretty much the same as that of my current traditional shaped 10" primary. The conical is also mounted using a single bolt through the back plate of the mirror cell, so that saves some hardware too.
I'm also using lighter birch ply this time (the old one is made from pine). Also, the 3 long steel bolts that hold my mirror cell are now only 10mm thick this time, the old ones were 12mm but that is unnecessary.
I've done various other tweaks here and there (the anchors with the guitar tuners are now as slim as possible etc).
I have excluded my whopping 1.3 kg 80mm finderscope from these calculations because this time I intend to make it detachable. I only use it initially to locate the target, so it's silly to have that extra weight sitting the OTA while imaging. Instead I want to create some sort of clip-on holder for it. Alternatively I'll just put a Telrad (~300g) on the OTA, but I really prefer using the big finderscope.
Cheers,
Rolf