I have a number of tripods (3 to be exact -- one regular mini, one flexy-leg mini, and one regular). I really wanted to use them for my huge zoom lens, but the the two smaller ones don't seem to be strong enough for my bulky lens... it just bends forward and points straight down. Any advice/tips/help on getting it to hold steady? Anything I can use to "prop up" the lens or reinforce the tripod so that it will hold the weight? Thanks in advance!