Ugh! Reading further I think that I see where you're headed: a single construction arm that simulates the kind of two glider constructions used by Gemini. That wasn't what I had in mind at all. I was thinking of using the elbow+hand method of construction that the Chapman-Greene arm appears to have been originally designed for. I must confess to being a bit of a n00b at the UCC thing and although I've been privy to a lot of the discussion around these I haven't followed close attention. In fact, I've been guilty of paying practically no attention at all. I was under the (maybe false) impression that slow glider recipes had been found for all of the Spartan still lifes and that this is why they were so special. Then again, I suppose that if that had been achieved, someone wouldn't have been able to resist the opportunity to build a self-constructing UCC before Gemini appeared.I could do that, but it wouldn't be pretty. At all. It would construct temporary constellations of blocks ...
BTW where does the "Standard Synthesis Library" in your synthesis script come from? It doesn't exactly match the Gemini constructions. I ask this, because whilst composing a Gemini recipe for a NE firing SS gun/"slide puffer", I used your script to give me some help at working out a construction sequence for the SE glider injector/reflector. (The NW variant is almost identical to Gemini's x_gun_1 but I had to roll my own for its reflection) At one point the script used a messy looking reaction to create an "fh_ene" and then later used a different reaction involving a pond intermediate to create another one nearby. I specified an "fh_ene" in the YAML file and got the pond-based reaction for both. This is Gemini's default and supposedly quickest reaction. Have you derived quicker ones?
I'm not sure about 'slide puffers'. Puffers are supposed to move. Something involving 'factory' would probably be more appropriate.Yes, the SS linear-growth patterns (henceforth 'slide puffers') could be produced collinear to the Gemini, with the line of blocks extending infinitely northwest.
As far as the output direction goes, I have already expressed my regrets at the unfortunate direction that I chose. SE or SW also works for an MSS pattern if we place the SS gun/slide puffer/whatever-we-call-it somewhere where it can be activated by a glider fired by the destructor gun of a decendent Gemini. NE is the only direction that introduces difficulties .
Never mind. I have been doing some 'out-of-the-box' thinking (this is also a direct reference to my long-winded explanation of Gemini's limitations above) and have realised that there is no reason why a static Gemini's elbows can't travel faster than c/580.