Is there a way to determine what size bed struts?

[MarkEHansen]

We have a Keystone Cougar 2019 26RBSWE with a king-size bed (RV Short King) with the lift-up cargo space under the mattress.

We're getting ready to install an upgraded mattress and would like to replace the gas struts which hold the cargo top up/open. The problem is I don't know which weight (or however they are measured) to get.

I would really like the cargo area to remain up/open without having to manually hold it (or use a brace/stick )

Is there a way I can determine what is needed by determining how heavy the lifting board is?

Any other advice?