Update: LTO is enabled by default for avr core/board version 1.6.12 and newer.

@scalz - You're right. There doesn't seem to be an issue with mouser. I must have gotten hooked up with digikey and some of the smaller sellers. I have a contact ticket open with mouser and the manufacturer for one of the models, as they can't tell me what the code means and the datasheet doesn't specify it either. Will post back here with what the order code "988-AT25DF512CSSHNGU-B" means. The minimum order is £33 for me at the moment, I seem to remember this being a little higher last time i checked, so not sure if its a limited time thing (worth a look if anyone wants anything from there). Is anyone in need of these ICs as i would order some for you and post to you if you just cover the cost of the item and then the postage for them (more than likely cheaper than paying for postage from them at £12 per shipment, to the UK anyway).

BTW, I like how you both made a case for it. Very nice!

@koresh Package went under the "Postnord" radar! Woohoo, perfect! I will start replacing the old capacitors and finally be able to deploy the sensors. Very nice of you to include some product samples as well. Really excited about these sensors!

@MiKa which box are you referring to? Generic boxes are available here: https://www.mysensors.org/store/boxes

@fets So far, I have only built the 5x5 board (but the others should be schematically identical). The only issue I have found so far is that I cannot get the ISP port to work. But I have checked and I have an identical setup on the 1.0 board and that worked, so I suspect the programmer is too weak to drive the net on this one. So it is not a board-issue per se, and might only be an issue on the 5x5 board as routing is the most complex on that one due to the size.

@djbonet you’re welcome. If I remember correctly, the datasheet diagram shows the limit for 8MHz to be 2.4V