Phantom, instead of magnets may do like I did on my Champ.
My top is held to the bottom with three CF pins.
I glued an old left over GWS part into the rear bottom fuselage for a pin locator, and a CF pin to the top half to lock in the back.
Then in the middle and front I glued a piece of foam inside the top half.
Reassembled it. And took a sharpened piece of control rod through the side of the bottom fuse, the new foam, and out the other side. Used those holes for locators and glued in a piece of control rod tube in them for strength and to keep the foam from tearing. Two short pieces of small CF rod with a piece of the control rod tube glued to the end to make a stop, now go through the holes in the bird.
Adds almost nothing weight wise.
Keeps the halves nice and tight, and I can pop the two pins and remove the top in a couple of seconds. No need to worry out using tape and peeling off the paint now.
Here's some pictures to give you an idea. Mod it to suit.