Replying to Portable drop-in plans

i built a portable drop in for urban and stuff a while back, and it lasted one hit, then broke. does anybody know a website, thread, forum, or anything that has plans as to how to build a sturdy drop in? or if you know, could you post here? ive built a bunch of skate ramps, and im sure i could figure this out, but are there any secrets to it that make it real stable? like angled out back legs or anything? any help would be appreciated

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