Yep build the mdf portion of the box first except for the back panel. You will need a couple of mdf rings to mount the subs. You simply position your mounting rings where you want them. I usually use a couple of screws to hold them in place. Then stretch the fleece over that portion of the enclosure. No need to cover the rest. Then resin the fleece. Now you need to build up on the inside ( the reason you leave the back off the enclsoure) of the fleece. You need to use mat and or cloth to buildup. Resin by itself is pretty week. How thick depends on the size of the panel and how much power. The more power and or larger the panel the thicker it's going to have to be.
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