Bill wrote:

I've been dithering about buying a high lift farm jack type device for a
couple of jobs, one of which is pulling a boat upright on a trailer

I've carried Hi lifts for more than 20 years and they're not very useful for
pulling as you tend to use a lot of the active length in taking up slack. I
also have a 5 tonne chain and ratchet winch which is much more controlable.

Hi Lift jacks do require a lot of care in use because of their inherent
instability.

AJH