That's a tricky task. I think the big three issues would be heat, weight, and mobility. If you can reduce body heat, make the armor light weight, and wear running shoes instead of boot armor, you should be alright. I think the best time to do a 5k would be sometime in October.
Heat can be beat with vented pieces and bright colors. (Black turns light into heat, and white deflects it.) Helmet fans are a requirement. Weight depends on what the armor is made of and what you bring with it. If you made your armor out of EVA foam, you should be alright. Mobility is the big one. Unless you have a spacious H5 suit, you'll have a tough time. The best thing you can do to your armor is replace the chonky boot armor with running shoes.