Novice builders should build the Left [power tubes left] amp to familiarize and then do the Right.[/quote]
Two things with that statement ..
1. It costs LESS to have 50 chassis made up of one type than it does to have 25 LEFT and 25 RIGHT chassis made up. You would add about $20 to the cost of each chassis. Since you have TWO chassis, a pair of M-125's would cost about $40 more. To "just bend the chassis the other way" would also add to the set up time and increase the cost of the amp.
2. The assembly manual is written for just one type of chassis and does contain references to the "left of" and the "right of" which would only pertain to a single type of chassis. This could confuse the builder.
The VTA amps are high quality "do it yourself" type amps that give great sound at a reasonable price. Having mirror image chassis would contribute nothing to the sound of the amps. It would only add to the price and could could cause confusion during the build of the amps. The Dynaco Mark III and Mark IV monoblock amps did not have left and right handed chassis and I never heard anyone complain about them ?