so i took apart my three neotats today-two had the larger holes n two small dents in the slide and one had no dents and a smaller cam hole-there is also the one with the smaller cam hole has more metal in the back frame-the top has a hole ported out for the motor wiring-the larger cam ones has the top backed milled out instead of a porthole which makes it lighter-.
So one is 2.5 with the smaller hole and one is also 2.5 with the larger cam hole but they both have different slides and the cam counterbalance is bigger on the larger ported one yet its the same size stoke-also on the smaller ported one the motor seems alot slower at the same voltage and is unmarked yet is all original.