The Nationals site webpage indicates that the fieldhouse to be used for Wright Stuff competition has a ceiling height of 25 ft. - 32 ft. It appears from the picture that the 25 ft. height would be to the underside of the nets that are suspended from the ceiling and 32 ft. may be the height all the way to the underside of the rafters. It would be nice if the event supervisor would explain and detail this on the Nationals website.
Without any additional information from the event host, you would be well served to prepare for flying under the nets at below 25 ft. as a worst case scenario and also for flying as high as 30+ ft. should Wright Stuff be in the section of the gym without nets (if I am seeing correctly in the picture). As hitting netting like this can potentially cause a bad result, you may want to plan to go no-touch for the first flight under netting and possibly more aggressive on the second flight. It appears in the picture that there may not be any ceiling netting in the back half of the fieldhouse. If Wright Stuff is to be flown in this section of the site, and you don't have a 32 ft. ceiling site to practice in, you could do partial motor testing to determine the best combination of prop pitch, rubber x-section, launch torque, etc. You could fly at 2/3 motor in a practice location that allows a 20 ft. climb in order to estimate flight character at 30 - 32 ft. of climb.
If Middle School Elastic Launch Glider is flown in the same site at the same time as Wright Stuff, the gliders should of course be given the section of the gym without netting (if there is a section without netting) as glider launch hooks tend to get caught in netting pretty easily.
Good luck and keep testing,