We (Golden) have done a lot of testing of our products onto Dibond and for interior works feel confident in the adhesion of our acrylic Gesso to the scuffed surface of Dibond's panels, which normally have a white polyester coating that should prove to be quite stable. As for you concerns with bonding primers, there are always risks when using commercial materials but keep in mind that Dibond itself - and for that matter any metal substarate - is de facto a commercial product. Commercial in and of itself is not a death knell and I think it is a misconception that all art material companies do extensive testing of products to assure longevity. The best of them hopefully do, and we certainly devote a huge amount of resources in that direction, but in general I would wager that high quality commercial products probably are tested more and more strenuously - and based on a host of ASTM Standards - than most artist coatings. I say all of this just to challenge the conception that artists materials are always superior. The best of them can be - and certainly the best companies will take pains to create the materials from well-understood components with an eye to longevity and durability. And certainly when formulating an art material you are thinking of a product's service life in terms of centuries while a commercial coating might be measured more in terms of decades. I just think it gets complicated and one can never make a blanket judgement of 'art materisls good' and 'commercial materials bad'. And when dealing with various commercial and architectural surfaces - like cement, brick, metal, etc - commercial products will often be much more specifically engineered and optimized for that material. Art products, on the other had - including acrylic Gesso - tend to be designed for broader, general use rather than very narrow targeted ones.
All that said, I think for your current needs there is no reason to go that route, but just for future reference, the ones that we have tested and recommend are Sherwin Williams' DTM Bonding Primer as well as X-I-M's UMA. We tend to recommend those over acrylic gessos especially for anything outdoors, like murals, where extreme conditions are common.
Touching on the AMIEN position about the expansion coefficient, it is true that there is some support for that but in truth the expansion and contraction of a Dibond panel is miniscule and negligible. Especially when indoors or if comapring it to wood or canvas. I would sleep well on those scores.
Turning to adhesion and mounting, we would point you to this piece of ours on the mounting of watercolor paper to panel as really the process would be the same, just substituting in the Dibond for the hardboard:
As in all things, when taking on a new process, we would recommend doing a test panel just to make sure you are getting the results you want, and because reversing anything - should something go wrong - would not be easy.
On that note, have you given any thought to using BEVA film as a way to mount the pieces? It would have the advantage of being reversible. You can find information about this product at Talas or Conservation Support System, among others:
Kristin and Brian could probably help further with thoughts about BEVA's use for this type of application.
Finally, "hold out" would not be an issue in this case, when working with a softer acrylic medium such as our Soft Gel, which is what we would recommend. Hold out refers to the resistance of a very thick material to flow into the nooks and crevices of a surface, but rather just staying up on top. For example, if you spread a layer of our Extra Hevy Gel on a roughened surface, there is a liklihood of air pockets and places where intimate contact between the gel and surface is not achieved. The product by itself will not flow into those areas without being pushed in. In short, that is what hold out refers to.
Hope the above is helpful, but don't hesitate to ask questions if you have them.
Senior Technical Specialist
Golden Artist Colors