Right now my #1 question to sort out is should I run this at 3.3v or 5v? 3.3v has the advantage that transistors switch faster, and I'm an optimiser so I would like this. However I love blue LEDs and have just bought a thousand of them, these are on max current when wired 3.3v -> LED -> NPN -> ground without a current limiting resistor. Should I worry that the LED might short and so blow the lot? (yes I think so). Also my new carry logic uses a diodes ladder which would like 5v much more than 3.3v (at a pinch I could use 5v just for this). So what should it be, 3.3v or 5v - I have yet to decide.
[ I've been out of the country on a work trip so haven't had any time for this in the last week and a bit - some new Schottky diodes have arrived and I need to stress test my new memory cell - time to take a day's holiday I think ]
P.S. it seems that there is a maximum thread depth which is stopping me replying directly below some of the comments. As a result they are appearing above which does confuse the flow.