Camp trailer springs

I would be inclined to say don't worry.

We had a Camel for many years with a similar suspension arrangement and no shocks from new. We dragged it over plenty of horrible roads/tracks without a single issue.
If you put replacements on it's quite likely they would either break off again, or worse still possibly damage the chassis rails if they were made strong enough to last.

Having said all that, I have no specific knowledge of the Cub units.

Odog

The first suspension of any vehicle is the tyre size/choice and appropriate inflation.
Little thin tyres with not much section height and high pressures will cause lots of trouble. Caravan makers don't always get this as good as is possible.

You have no way of knowing if the original shocks were suited to the application or not and if the tyre size and pressures allow for a compliant ride.

If the shocks didn't close up enough and bottomed internally that would cause failure of the mounts.
The mounts may have been unsuitable for the shock action.

I presume the two rebound springs you speak of are actually coils to provide additional load ability.
I prefer to have shocks as they allow the wheel/axle mass to be controlled in it's action and dampen out unwanted and damaging oscillations of the suspension.
They stop the tyre being fired down on to the ground as it goes over a drop off or over sharp bumps.

I fitted Landcruiser front spring to my trailer and the with and with out shockers fitted is very noticeable. Without it bounces around especially when empty and with the shocks fitted rides controlled and smooth. Same reason a car or 4wd has them.

Correct length shockers fitted to suitable mounts will not break off the mounts or damage the chassis. It is more likely the fitting of shocks will reduce the vibes and harshness transmitted to the caravan body and the body work won't be unscrewing itself as you travel.

Of course this is your choice but I know what works. Without shocks, everything gets multiple unnecessary hits, where with shocks they limit the rebounding of the suspension to a minimum.

Ross M