The K&B was the old workhorse standard back in the day. The Thunder Tiger was dud unless people knew how to modify them and only one guy was good at that before he died. My first K&B 3.5 OB cost $115.00 through Tower Hobbies when they sold a lot of boat stuff..A hull was about the same price then.
The .21 OB tunnel classes have all but died in competition unfortunately. One district race drew 13 of them one year, the next they couldn't fill the class with 3 boats.
Your boat is one of the few mono's made for outboards as many others have tried over the years. At one point AquaCraft was ready to roll out a larger version of their Super-Vee 27 for inboards also but it never made it to production. Jerry Dunlap raced it a few times in competition.