Tower combo, Sig Kobra & OS 25LA...good combo??
Depends upon what performance you are expecting. The Kobra weighs in at about 48 to 56 ounces depending on radio and engine. I would gest that plain bearing 25 would put out about 40 -50 ounces of thrust. .......enough to fly it and pull it through a reasonable loop. It should come out on the light side, too which is good.
Mine has a ThunderTiger .36 which can pull it straight up while doing rapid rolls adding to the drag. But, it weighs the 56 ounces, so it has to fly faster.