I took a chunk of carpet, laid it in the trunk, traced it and cut it out. Didnt glue it, just a "mat" for the bottom of the trunk.
If you are looking to spend $300, I would spent $80 and just get the trunk bag, sew some velcro to the bottom and top of bag and attach to the trunk so that when you open, you have a multi-purpose organizer. You can take it out of the trunk when traveling or leave it in for those short trips.
12 CC Tour, Ness Atom Bombs, Stage 1 kit