Ken, you may want to consider making your own. I made some many years ago, have given several of these to close hunting podnahs and have 2 sets now. I'll try and describe it for you. Someone here may be more descriptive than I am, so please jump in and assist.

I go to the backpacker shop and purchase the fiberglass tent poles that connect to each other with an elastic shock cord within and I get 6, total, 3 for each side of the stick(s). Get the larger diameter ones. I buy from a auto parts store, some 3/8" rubber fuel hose and use it in 7" lengths for each set of sticks. What I do is the following;
1) lay out the 7" piece of rubber fuel hose and from the center of it, cut back each way - 1.5". This gives you a 3" long slit in the center of the hose.
2) bend the hose in a "U" shape with the slit on the bottom.
3) separate/fabricate the 6 fiberglass poles into 2 separate, 3 pole units (each with its elastic shock cord).
4) shove the 3 piece units up and into each side of the slit of the "U' shaped rubber hose and superglue them in the hose in the part(s) that is not slit, towards the top.

Now you have your shooting sticks that are just about indestructable, fold and store easily and can accomodate a 6' 2" shooter like me from sitting to standing positions. I transport and store them folded and secured with a thick rubber band with spare rubber bands around the legs. As you have surmised, you control the height by the # of units that you use and the natural action of the hose is to open the sticks which you control with your offhand, spreading to lower and squeezing together to raise. They make right good walking sticks, too. The fiberglass is easy to trim to 'customize' your height. My original pair is >15 yrs old and I've carried them to/from Ak, Mt., Wy, Co, Nm, Tx and wont leave home without them. Some have scoffed at them at 1st sight then asked to borrow them to make their shot with.

Just my .02$

Mudbug