I will add some notes about how shape combo works here as I'm developing.
Inbetweens and Combos - Actually this might not be an issue anymore.
Imagine we have a shape forward and a shape up and we create a combo forward_up.
Everything is working fine. However once you add forward75 inbetween things might not interpolate as expected.
Usually the combo would turn off from 1 to 0. With forward75, the combo will turn off from 1 to .75.
This can be a headache if you add forward75 inbetween before creating forward_up combo.
Because you won't get the combo fading off nicely from 1 to 0.
One strategy in this case is to create your forward_up combo first. Add it into the system. Then when you go to create forward75, the shape you get out will have some of forward_up mixed in.
Keep in mind that if you update forward_up after this, forward75 will not get the update automatically. You will need to sculpt the update into forward75 as well.
Inbetweens at values other than the defaults
By default Shape Combo system comes with 75, 50 and 25 inbetweens as options in the UI. However you can do an inbetween at any number between 01 and 99. You just have to name your shape the same as the hero with the number at the end. For example forward is your hero and you want to add an inbetween when the slider turns to .1. All you have to do is name your shape forward10 and add it in to the system. forward10 inbetween will be added under forward in the ui and be highlighted.