Room addition to the ToyBox

My project is a former Toyota Uhaul moving box truck. LIttle by little its becoming a camper. Last week I extended the frame and added a trailer hitch. Now, I'm working on framing and skinning a 24" addition out back.
The back of the box is thick aluminum extrusions...plenty strong. I'm going to use .060" aluminum sheet for the walls and some ~~.037" wall square aluminum tubing for framing the addition.
The next step will be to attach the whole works together. I'm wondering what adhesive with good sealant characteristics would be good to use. I'll use pop rivets for the most part but I still want to have bonding and sealing too. In this situation it's very unlikely that disassembly will be an issue.
3M 5200 seems to be one good choice...Sika makes a similar product I think but I can't recall the name.
ToyBox Tom
Pictures:
gallery/album.php?album_id=2415
The back of the box is thick aluminum extrusions...plenty strong. I'm going to use .060" aluminum sheet for the walls and some ~~.037" wall square aluminum tubing for framing the addition.
The next step will be to attach the whole works together. I'm wondering what adhesive with good sealant characteristics would be good to use. I'll use pop rivets for the most part but I still want to have bonding and sealing too. In this situation it's very unlikely that disassembly will be an issue.
3M 5200 seems to be one good choice...Sika makes a similar product I think but I can't recall the name.
ToyBox Tom
Pictures:
gallery/album.php?album_id=2415