The reason you got a poor response last time you asked this question was because of how you worded your opening post.
The answers you seek are not straight forward, but nor is it rocket science. You will benefit from using any form of lap joint that allows a degree of movement between the two materials. The amount of movement you need to allow for depends on your choice of construction, specifically the wooden portion of the shell. Solid wood forms will contract and/or swell more than a multiple ply forms. Also think about the lug forms, which portion they will mount on, or possibly straddle both.
Fit is usually via mild interference or "snug" when new, with the lap joint augmented such that the most likely shrink element is catered for. If you're just going to slice up some Keller shells & use tube lugs to straddle the joint, I wouldn't worry about a bond too much, just get a snug fit. You could consider using a bonding agent, but that carries risk of splitting if there's excess shrinkage of one element. Alternatively, some form of flexible bond or gasket can be employed, but that adds dead mass to a construction with an already inherently poor resonance profile. Fit between components needs to be snug in the long term, wether by bond or not, so as to prevent rattle/buzz issues.
Before doing all of this, consider wether you're really equipped to do so, or wether you're better off placing your money with a company who's already done the hard work, & is prepared to warrant that work.. Also consider why you want a hybrid shell in the first place. Have you a sonic basis for your decision, or is the main reason cosmetic? - It usually is.
