Have to agree about a custom actuator and it might not be much work. Using that GLA4000 as an example, it only has a 50 watt motor and I'd bet you a pint of Guinness that is fairly low RPM as well. By changing the motor for one with 4 or 5 times the RPM and maybe 100 to 200 Watts power, you would get the required force and speed without having to make an actuator from scratch.

Some random thoughts:

Using two actuators is probably LESS reliable than using one larger one. If a motor or gear fails, it will lock the actuator solid and the other actuator will be trying to twist the wing - either something mechanical will break of the 2nd motor will burn out quickly.

If you use an Arduino, this motor control shield might be a good match:http://tinyurl.com/bmp4lmy. It uses automotive motor control chips that have temperature & current limiting and should handle high power actuators. It will work with very little programming and has advanced features you could use at a later date.

What sort of budget are we working with - penniless student or rich sponsored/factory team?

The forces acting on the push rod and actuator are always going to be compressive, which is exactly how actuators are meant to be used. For the push rod, I'd be using a wider tube rather than a thin solid rod as it will deflect less in compression for the same weight. Add a million style points if you can use a carbon fibre tube.