The mechanical engineer in me has to voice my concerns over using bolts for the standoffs. Bolts are intended to be loaded primarily in tension and clamp components together or possibly shear where the two components are in close contact and under load are trying to effectively scissor the bolt in half. Bolts are not intended for supporting bending loads as are being applied in this application. Applying a load perpendicular to a bolt at an unsupported length will create bending stresses at the base of the bolt and bend it. Effectively the length of the bolt provides a lever to increase ability to deform it.
The calculations are pretty simple and, assuming that is a 3/8" grade 8 bolt, 3" long from where it exits the stick, it will only take around 145 lbs to permanently bend it. Make that distance 4" and the bending force is down to the 110# range. It's better for a 7/16" bolt where the forces are approximately 225# and 170# respectively. Considering there's 4 bolts this may not seem like a problem at first but consider what happens if there happens to be a knot or high spot immediately under one of the standoffs. That will create a situation where that standoff is carrying almost all of the vertical load of the stick. In that instance it would be pretty easy to apply enough load to bend the standoff. Once it bends it is possible that the stick could loose its grip on the tree and kick out. Best case you just end up with a stick with a bent bolt you need to replace.