Depending on the subs you are running and power, you will want at least 4. A set of JL's could need 8 layers so it does vary but 4 minimum I cannot tell from the pics what area is the enclosure for the subs. If its only the area below the rings; I don't think you will be anywhere close to the required cf for most subs.
Also, I'm concerned when you pull over the speaker rings, they will not take the stress and break off the dowels but hey, I can't answer that from here, you will have to be the judge of that. Also if your pulling to the edges of the plastic trim pieces, will it withstand the stretching? Is the plastic rigid enough? Just give all of these things consideration as you move forward.