I've always adjusted chains with ME, the rider, sitting on the bike, bike upright off of the stand.
Reach down, check slack, adjust, snug bolts, re-check, tighten, check again, done. An extra set of hands helps if you haven't done it this way before.
If you adjust it on the side stand, and according to the owners manual; that means that the chain is set correctly for the 150lb rider, and the 250lb rider...until they get on the bike. Then everything changes.
Too loose, chain rattles, wears out faster, can come off, causing damage and/or a crash.
Too tight, chain pops, wears out faster, can break, causing damage and/or crash. Not to mention the rear suspension cannot function correctly. And, if the rear suspension can't work right, it's going to throw off the front and overall handling also.