i use 2 servo screws through hobbyking velcro and a strap- except on small foamies, the hk velcro enough. if you've never used it, try it. strongest grip i've found. a meter by 75mm for 4 bucks. https://hobbyking.com/en_us/polyester-h ... s_products
i don't like their black battery straps, they separate. i buy velcro brand of those.