My husband was the brains behind that project. The springs are Hillman brand 10" tension springs There's a close up pic at post #19 of all the little parts and pieces that Joel put together from the hardware store. Later, he saw the ready-made version called the Attwood Hatch Lift Spring at a marine supply.
friend Frank found the RV Designer H271 Springloaded Cabinet Door Struts. We had one more cabinet (that we forgot to count when buying springs) so we used a strut there.
The spring supports the door then closes with just a tap (or inadvertent bump) The struts hold strong then snap shut pretty powerfully. Advantages to both, imo.
Hope this helps!