I created Simulink model for Contacts message and able to subscribe Contacts message data. To enable this, I did following changes.
1] The Contacts message is repeatative so you have to change few messages as follows.
You should change Dimensions as per you message length. Also, don't forget to change DimesnionMode to 'Variable' ( Highlighted in red ). The contacts message keep changing its size so it should be variable. Make sure, you do all following changes.
2] The Simulink model look as follows,
Basically, you we get values in array form. e.g. If Contacts message contains 14 Contact messages/details, which you see as repeated fields in protobuf but in Simulink, these messages are in array form as shown above.
In above figure, <x> contains Wrench.force.x in array form, in which, each index define force.x value for each body.
You can separate these values in MATLAB function.