My 50 cc DA pulls a 17 lb plane vertical with enough authority to do unlimited sequence in IMAC. It probably is pulling in excess of 25 lbs. of thrust.
In order to do as well a 26 cc engine would have to be in an airframe at 8-9 lbs all up weight. Not many can make the weight requirement. Most 26 cc engines are way to heavy to make this possible.
I met several guys in Texas who were flying 25 cc gassers in the Sig Four Star finished out at about 14 lbs. With about 13-14 lbs thrust they made good sport flyers and would handle IMAC to the basic level, marginal at the sporstman level.
A 15 lb Aeroworks 540 29 % with the DA 50 would go vertical like a rocket and is quite buildable. Arthur Cloutier