I have ordered a Neewer 50 cm (20 inch) mini tripod for my Canon 750D and EF 70-300mm f/4-5.6 IS II USM lens. The tripod is suitable for up to 5 kg. However, I am not sure that the weight is the problem, most probably the problem will be the length of the lens when at 300mm, which is when I need a tripod the most.
Note that the lens does not have a tripod foot.
Are my worries unjustified, or is there some other accessory I need to balance the camera and lens on the tripod?