Easiest:
#1. Park the front tires up on 2x6"s or 2x8's(either one or two staggered) cut down to size. That will lift the front end and get the spoiler out of the way for your straps.
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Yeah, that's something I was thinking about as well. Especially since I have the risers already built up from the lowered Z06 (now gone but was needed to get a jack underneath).

Do you have yours attached to the trailer floor or are they loose.