Some good responses here already. Unless the 'browse line' prevents me from going higher, I try to NOT hunt in a climber at 15 feet or less. I prefer to be around 30 feet. 20 feet is good, but the canopy can start messing with you above that. Plus shot angle can be a factor. Ultimately, your biggest obstacle is stand safety. As SprintFlyer stated, your stand can flip though the cables if the tree becomes narrow and your stand points downward too far.
If your new to climber stands, I recommend that you use an ascension rope and harness while climbing to your desired height. This will prevent you from falling should you be ejected from the stand because you "flipped" the cables.
Stand platform should be 90 degress to the tree ideally, once you have reached your height. So set it up a little bit more acute at the base to compensate for the larger trunk size. Like 70 degrees or so (your feet should slide toward tree while on the platform and facing the tree at this angle). If your climbing and the angle of the platform to tree becomes greater than 120 degrees (feet are clearly sliding away from the tree), there is a really good chance that you are about to flip through the cables.
Remember to FIRST always hook your harness to a tree strap once you reach your desired height.
BTW, I bough the Summit Razor SS last year. Same thing as your Viper, but with a drop down bar for bow hunters. Man I love that stand! I can sit in it all day. My Lonewolf is nice too, just hard on the butt after 3 hours!