Interesting how some one innocently asks for advice and the thread always seems to end up in a shit fight.
Also interesting the definitions of hydraulic lock .
If a closed container like a shock does not have enough "free" volume . ie gas volume .to allow the shaft to travel into the shock of course the shock will lock , or most likely the seals will blow out to allow the shaft to continue , or the shaft might give under the pressure and bend but that is not hydraulic lock .Hydraulic lock can in theory happen in a shock and is not really dependant on free volume in the shock to which allows the shaft to completely travel into the body its full length.
Its dependant on the volume of oil that can pass through whatever dampening oriface or restrictive passage there is for a given time.
Early prolink shocks had very small pasage for oil to flow from the shock to the res. The shaft wasnt that big but on compression the oil that it displaced was too much to travel from the shock to the res. This created what the mag testers called a "mid range spike" , its not really true hydraulic lock .
If you compressed those shocks by hand you would never feel it because you cant compress the shaft quick enough - the oil goes through at a relatively slow speed but hit a big whoop on the track and the speed and therefore the volume of oil per sec trying to get through was a problem . The mod at the time was to bore out the holes in the shock and the res. and this helped solve the problem.
The oil displaced by the shaft into the res. is regulated by to adjuster or hole at the res.and the shaft diameter ,bigger or smaller is relative to it.
The main valve in the shock isnt affected by the shaft size but by the speed at which the shaft travels into the shock body.If the holes in the main valve are too small for the speed and volume of oil then "hydraulic lock" or "mid range spike " also happens.Both terms are not really correct IMO its just over dampening.
note ITC ohlins used an hydraulic lock type valve at the end of the shaft to help resist bottoming, similar to the bottom out cones on your forks- modern works and aftermarket suspensions use similar setups.