The first time I glued panel brackets on with sikaflex-11FC, I got cold feet and ended up puting a bolt through each bracket. I have since added extra panels with no bolts. I have however thought of installing one ring securely to the roof and tethering all the panels to it with stranded stainless wire. In the case of a glue failure, the panels would be restained.
Trevor
NZMCA member, 2005 Canter 3.6l. 370w solar. 220AH Gel house,195l Fresh/150l grey. VSR,12v Equaliser charger, 7 stage 240v charger, 1000w mod sine inverter, 300w pure sine inverter, 12v Vitrfrigo 90l fridge. Webasto diesel heater. Thetford WC.