Bemo queries

I bought a Bemo start set today and have a few queries;

- is there any way to improve/change the couplings as the standard ones are a real pain in the neck.

- some of the wagons "wobble" when under way. Looking underneath, there is play in the plastic parts that support the axles, maybe to allow easy swapping of wheelsets to HOe? Is there any way of firming these up so my wagons don't wobble off down the track?

The models themselves are very nice and easily upto Brawa standard with many separately applied details including metal handrails etc.

thanks