it is set at 15. Well, more like 13 in my car, at least. I'm looking for "engine off shortly after your foot leaves the gas pedal at any speed."

I don't think we need more acceleration, but a larger IMA is always nice for the other reason you mentioned.

The IMA in the HAH can have a different usage than simple assist- it can allow the ICE to remain on 3 cylinders during harder climbs and to handle other accelerations. That is a quantum step, literally, beyond simply assisting in a linear manner.

It is pitifully difficult to stay on 3 and accelerate in any but the slowest way, and IMA assist in 3 cylinders is touchy- very very sensitive to pedal pressure and it quickly just flops over to 6 cylinders. Climbs are very doable on 3, but a larger IMA would allow more speed to be maintained while keeping the ICE load constant.

So while I don't like using IMA very often, if it were larger it would make it far easier for the driver to remain on 3 cylinders over a wider range of conditions, instead of calling on 6 for a slightly-too-hard situation that only last for a few seconds.

--> My ideal HAH would be a 3-cylinder car that happened to have 3 more available for those few times you actually need >100HP. Instead of sometimes going down to 3, the system would be biased towards 3 as the normal state and 6 as the "assist" state, even at startup from a stop. The same overall performance if you want to use it, but the 'preferred' condition would be more efficient.