I am designing an experiment whose main app, for individual decision-making elicitation, has 60 rounds and 5 apps (one for each of 5 between-subject treatments).

Is there a way to avoid creating player[round].myfield for every round, and limiting it to, let's say, rounds 1, 21, 41 and 60? Otherwise, the database gets full of surplus columns of blank cells.

I have 5 treatments that require too much custom JS calculation on the client-side and different layouts for multiple sliders and text content, thus I also need 5 apps X 60 rounds X 9 player.myfield instances = 2700 columns.