I use the velcro battery straps and strap them under the chassis. I used a piece of lexan for protection. You can see it in my profile. I've never had a problem with these straps. I have a set that came with some batteries and also some Gorilla straps. Just make sure you've got them tight. By the way, under the FLM Ext.Chassis you can fit 7-cell stick packs, maybe 8-cell sticks but I haven't tried them yet.