Physics of Minecraft derivation - the graph is unwieldy

There's a video on the Physics of Minecraft which measures the gravitation in Minecraft. I wanted to see how well the projectile motion is described in the Physics Derivation Graph.

Screenshot from 0:35 in the video. Useful commentary is on news.ycombinator. The post on Wired.com was basic.

On paper, the derivation was 4 expressions and two lines of text. The Physics Derivation Graph yields a cumbersome 7 expressions and a total of 25 nodes (feeds, expressions, and inference rules).

Current output from the Physics Derivation

The reason the graph is large is because the "subXforY" is used three times. Analysis of the midpoint is really three concurrent substitutions: at y=y_mid, v_horizontal=0 and t=t_midpoint. Concurrent substitutions are not supported, so three steps are required.

Also, the current implementation lacks support for comments.