I just wanted to touch on this issue again that bootleg has already covered.
But trying to incorperate his 2 different posts together

By using a bar line up the top both OH and OH damage can be recorded.

- Full line (light)= the amount of OH you start with
- Second colour (dark) = how much OH you have currently have available
- Arrow = decreases as more OH engine damage (loss of endurance) is caused and
where
your OH can restore to. (in the same way as the health line works with reps and SD.)

Bar description text can be added as an optional.
Bar colour can be blue, black, yellow or what ever colour suites best

Depending on the backend code used this bar should be quite easily implemented
with out
restricting any other options, features or GUIs.