? I don't see how the weight of rider and gear can compress the isos.
I'm surprised you make this statement OK if you never thought about a commando's dynamics. I would not expect your question to be as a troll.
The thrust analysis due to load is as follows:
A featherbed rear shock angle is approximately 12 degrees, BSA A-65 approx 18 degrees, commando is approx 30 degrees.
A load on the bike frames, primarily the rear, causes a rearward thrust.
Take your rigid bike. Disconnect the chain and rear brake cable/rod. Remove the rear swing arm bolt/shaft, insert your fingers than drop the bike with an added 500 lbs. Any idea why your fingers were cut off? rearward thrust is the answer.
On a commando the shock absorber rearward thrust load triangles are 3 fold. front iso, rear iso, top iso. Top iso is eliminated with the DT head steady.
the three iso's all contribute to restraining the load from the horizontal thrust from the rear shocks. The thrust will be at a rate of sine 30degree X verticle load. A 500lb load makes 250 lbs rearward thrust. The 3 iso will share in resisting this thrust. The normal frame is the obvious 3rd leg of the triangle.
Rear thrust is always demonstrated on a commando with no engine or tansmission when only the rear iso is supporting the cradle. The rearward thrust on the cradle by the swing arm which is below the iso support makes the front of the cradle push down pivoting around the top rear through bolt.
More weight makes more load therefore more thrust through the ISO's and the rubber will deflect more. see chart in post#6