The bar is not the worry or problem in my humble opinion. The real problem is if the deer comes up behind you !!! Try shooting a close shot right behind you <10yds. It cost me the biggest buck of my life and my son missed his first trad deer too. His lower limb hit the upright on the seat during the recoil of his lower longbow limb. On my buck I could not even get close to full draw. Could not fully extend my bow arm without the bow hitting the upright. It was all over in about 2-3 seconds, just had no shot and he moved on.
I hunt out of my Viper all seasson and during bow season I simply put the upper part of my Viper a little closer to the platform which gives more clearance. Makes sitting a little less comfy and your knees are a little higher than normal. Takes a little more effort to go from sitting to standing but can be done.
If a deer comes from behind and it is the only shot you have then try stepping as far away from the tree as possible. If my son would have simply took one step away from the tree and toward the front of the platform we would have had backstraps, no doubt. His deer was about 16yds away. Hope this helps someone else not blow or miss a opportunity. I love my Viper, other than that one issue.
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