There are several versions of Sikaflex designed for different types of job. Some are just sealants (bloody strong sealants) and others are adhesive sealants (very bloody strong adhesive sealants). I use Sikaflex on a regular basis, either 221 or 521 dependent on the job in hand but to be honest either will hold anything to anything if the prep is done proper like
. If you're sticking alli then it needs to be ultra clean so stainless steel wire brush the areas to be bonded first then chemically clean with a solvent, then apply the Sikaflex and finally fit the panel. It will be a huge help if you can preform the panel before applying the Sikaflex as it will reduce the need for fixtures to hold it in place while the adhesive cures (can be up to 48 hours dependent on type and temperature/humidity). PU adhesives like Sikaflex are moisture sensitive so damping the glue with a water spray can speed up curing times.
Google Sikaflex to find the best one for your needs.
D.