You will struggle if you are using the hobbyking rams because they are so small, diameter of maybe 4mm? not sure how much pressure you compressor makes? like acadieman said you would probably need a tank for it to work better. Here is how it can be done hydraulic using similar valves to the ones you have, wont be very precise though
http://umstech.in/admin/Uploads/pdt_...012kg%2003.pdf