Some of my eBay orders arrived over the last day or two, namely the plasticard and the sheet magnets.
The plasticard looks a lot thicker than the advertised 2mm but upon measuring it is indeed only 2mm thick. Anyway it's sturdy enough and it's black all the way through so I won't need to paint edges (hooray!)
The magnets are bang on 20mm x 40mm so they fit Warmaster bases perfectly, no trimming required.
They add very little to the depth of the bases and the strength is quite good considering that sheet magnets aren't known for their strength, although the Carrion probably isn't the best test as it's a pretty light model. Then again I don't need the magnets to stick the minis to my fridge, I just want then to stay still on movement trays and in storage. Quite pleased with these overall, I may just have to order another pack or two and do all my Warmaster stuff too.
I'm a little tempted to start cutting the plasticard into Warmaster sized bases now so that I'm ready to start as soon as the Pendraken stuff arrives. Maybe I will for the infantry bases but I should wait and see how the tanks fit first.