Inlay Style Trunk and Door Panels - Need Help & Ideas

[The WidowMaker]

im going to be starting the interior on the chevelle and need some help figuring out how to build the panels. id like to do an inlay style panel (1st pic below) and have an idea on what id do, but id rather not reinvent the wheel and end up with a longer process on top of it.

my idea is to start with a template of the inlay piece. with this, i can use the router and bushings to cut a hole in a 3/8" piece (the main panel) and cut another piece to inlay out of 1/4". since the 3/8" piece would be cut all the way through, i would need some sort of backer to attach the inlay to with (velcro?). for this, id just use a piece of 1/8" mdf that i would bond to the back of the 3/8. in the end, i would end up with a 1/2" thick piece of mdf with a 3/8" deep cut and a 1/4" piece to inlay in the hole. i thought of starting with a 1/2" piece, but i dont want to route all the inside out to 3/8" deep.

the questions; is there an easier/better/faster way to do this? what gap should i leave between the inlay and the hole? my thought was 1/8" all the way around which would probably end up at 1/16" after putting leather on it. im also thinking that the 1/4" inlay with fabric folded around its edges and back plus the velcro will make it stick out the extra 1/8" to be even with the 3/8" deep cut. is this an accurate assumption? is there something better than the velcro to fasten? what sort of glue should i use that i can spray from a gun? ive read that landau (sp?) is good, but cant find it in anything less than 1 or 5 gallons.

second issue. for the rear shelf i need to build up the depth a little to mount my speakers. they will also be in a cut out section and have an inlay of speaker fabric or some sort of grille over them. since i dont want to run a full sheet thats 1" thick, i want to build up the edges around the inlay and leave the rest of the panel thinner (kind of like second pic). whats the proper way to do this. ive thought about cutting my own mdf in the shape and size i want, but that too is tons of work. hagan street rods sells a foam that will do the same thing (3rd pic), but its expensive and im not sure its the size i want. are there other foams like this? any other suggestions? Clint, Tracy, i'd love your opinions! Thanks!!!