Website for testing theoretical stats for future Pokemon?

I am aware that there are sites available that simulate raids and give the results and performance of specific Pokemon against specific bosses. However, I was wondering if there was a site that allowed for the custom input of stats for nonexistant Pokemon, but using existing moves and raid bosses.

For example, if I wanted to see how a Regigigas with Rock Smash and Focus Blast performed against a Tyranitar raid boss, is there a way for me to create a custom set of stats to use in calculation?

Any suggestions would be greatly appreciated!