I am fairly new to outdoor photography but I am really enjoying the hobby. I am planning several trips this summer, one to Yellowstone. I have an XSI and plan on using my Sigma 50-500 on the trips. I am looking for a good, portable, sturdy solution. Since I will be flying I would like something that can collapse to a small size yet be strong enough for the weight and the rigors of travel. I am not interested in the expensive carbon fiber type units but a more reasonable priced unit would be great.