My 2X2X2 also used the motors as brakes - the return oil is piped through a valve that simply blocks the flow coming back from the motors (effectively turning them into pumps). In a similar way to electric vehicles - hydraulics can also incorporate 'regenerative' braking by storing oil pressure in an accumulator, but the valving involved is complex and bulky.  Imagine though if a road race bike could store even 50 % of the braking energy from the main straight….

Though a clever idea, the hydraulic braking unfortunately created much higher pressures than the drive and blew the pivot seals out regularly, the simple fact is that so much energy has to be dissipated in such a short space of time that this method is not suitable.  This represented a major sticking point in the development of the bike as it precluded any high speed work, if the project was to be developed further an alternate method of braking would have to have been adopted.