With 2 up and some shopping in topbox we are near to if not just over the maximum load of 198kg and the shock bottoms out on uneven road surfaces. So my question is whether i should consider upping the load of the shock with a new aftermkt shock,or not to go shopping ? Being rather keen on maintaining a middle aged portly frame i am asking for some advice . Thanks.

Have you wound the spring preload to it's maximum?
If so, your next cheapest option is to have the spring on the standard shock replaced with a higher rated one.

The original Yamaha shock is robust and very reliable. Purchasing an expensive after market shock to go shopping seems like overkill to me

thats good advice thanks a lot