i would use some sort of cushion for 2 reasons... this can range from foam insulation, to pool noodles, to a towel.
1. prevents any more scratches. (the more you can prevent, the better)
2. keeps the yak in place. (i've seen yaks slide during transportation due to no friction under them.)
so all in all.. you could always zip tie a towel onto the bed extender. i've even duct taped pool noodles to it before. the extra padding helps out A TON for transportation
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