Curtis 1204 60v survivability, anyone dissect one?

My folks have a stock 48v mini van (Miles ZX40) we have upgraded the battery pack to a new old set of 6v Greensavers.

They perform OK (capacity wise) but seem to not output amps at a high voltage for very long which affects the top speed quite quickly once we burn of the initial charge.

I am curious there were several individuals running Curtis 1204 48v controllers with 60v (one was in a Miles identical to mine) However his voltage was generally at or below 60v due to the type/condition of the batteries he used.

I am curious if I could "Get away" with an additional 6v, 8v or best yet 12v battery that I would "switch in" once the batteries initial charge was burned off.

Also how do I setup curtis F/R contactors to "Switch in" an extra battery. I would prefer with no power to the contactor for the 48v path to stay put, with power applied to the contactors switch to 60v.

Anyone ever dissect a curtis 1204? They seem relatively reliable although underpowered, it may be a very simple mod to upgrade one to 60v (incorrectly), since they are a dime a dozen I could get one to play with and likely replace mosfets and diodes if necessary. I do no believe the control circuitry at 60v is massively effected as most 12v circuitry isn't hurt running at as high as 18v normally. And the caps if I remember "should" handle 60v after the pack has been run a while.

Anyone ever get ticked and do this to a 1204? How long did it survive?

I have also thought of just adding a single 2v cell to the pack, sadly it couldn't be a greensaver but likely it would allow the controller to survive.

Anyone have any comments on 6v greensavers and the curtis 1204, looking for a been there done that, I have a feeling the abundant 1204/1205 models would be excellent platforms for cheap voltage modifications. Especially for those of us who do not care about performance paticularly but would benefit from higher voltages.

Cheers
Ryan