I use the Predator IV pendulum and when I started using it it was the only pendulum sight that had an adjustment for arrow speed. Might still be? When it is set up properly, it's dead on no matter if I'm 30 feet up or on the ground or anywhere in between and even strait down. The only yardage I need to know is my max yardage, 40 yards. No compensating, no guessing, no expensive rangefinder, no yardage markers, no extra pins to be confused by, put the pin on the target and shoot. I've used it for 8 years, have killed many deer and other critters with it from a lot of different elevations and it's never let me down. About the only thing I haven't changed in 8 years, it's now on my 5th bow.
No matter what you use, practice the same way that you intend to hunt. A few practice arrows from the tree stands will eliminate the doubts you have and hopefully give you more confidence. We used to always take our bows out before season and shoot a few targets while fixing up the stands, trimming lanes ect. Great way to get the guys together preseason and have some fun while getting some work done too. Using a 3D deer target on these outings also added to the fun and we actually learned a lot about hitting the angles to the vitals. IMHO using a 3D deer target should be required before any archer is allowed to deer hunt. Good idea for every species that anyone wants to bow hunt. Learning to shoot is not enough and useless if you do not know where to aim. Unlike a rifle or slug gun, you're arrow path to the vitals has to avoid large bones, so your windows to vitals are much smaller. From a tree top, your angle may not allow a path through more than 1 organ. If you miss the heart and get just 1 lung, you chances of recovering that deer are slim to none. Ideally you want to be up high enough not to be seen but low enough to get a shot angle that can effectively take out both lungs and the heart in one line. If you need to climb up to 25-30 feet to see deer, maybe you should try sitting still or changing your scent control routine, or maybe just stick to fire arms. I understand the urge to climb way up there, the view is awesome, you're on top of the world, we climb mountains because we can.....what ever. If you're out to see deer, stay up there. If you want to kill a deer, your odds and shot angles are better closer to earth.
American by birth, hunter by choice.