When I really gave Sum4 a solid go the first time, I was building the monomers two atoms at a time.  This got me some relatively fast inputs, but construction was convoluted- it either took a long time, or was expensive with arms on both sides of the polymer to get everything in place--not really ideal either way. Eventually, I took a closer look at the monomer and noticed that building the polymer would be relatively simple with sticks of three.

My first attempt with this build order was only about 15 sum4 worse than my  previous current best, so it seemed promising. My first solve with this build order was held back because it had to deal with the fire atom sitting around until the vitae/mors showed up.  So, I decided to sacrifice the seven area at the end and build the fire stick first. This ended up filling up a fair amount of space on the tape of the construction arms; nearly lining up with the time it takes for the input arm to handle the input and generate vitae/mors.  Well worth the area trade-off.

Overall, I really feel like I learned how to discard approaches and pick up new ones.  I don't think I would've caught onto the stick method if I were shown this puzzle two weeks ago.