Absolutely legal and in no way tricky, just a smart way to prevent others from stealing your ideas before the stream starts!Tricks:
Some contenders do not want to show their creation before the event starts. This is very reasonable, as weak spots hide in every design and some try to find those before the battle starts. If you don’t want to upload the png of your tech in this thread, you can get into contact with the announced streamer via PM and send him a link to the png. Make sure to post a picture (no png) of your tech here with the name of your tech and the league to compete in, to make an official entry. Please make also sure to send your png early on, so that it can be loaded by the streamer before the stream starts.
You can always test your techs against all others when they did become champion and be the next champion one week after that.
Btw. some consider it cheap tricks to test your tech against all others challengers and refine it until you beat all, so ... do what you need to do, but it would be a shame to lose you and your techs for sumo.
One last thing: A real champion and a real brilliant builder comes up with a tech that beats all champs and all other challengers without knowing what he is exactly up against in my humble opinion.