Sir,
I believe I know why you might think that using the cockpit section and modifying the torpedo tubes from the AIRFIX Vosper and using the hull from the Revell PT-109 kit COULD result in a post-war Soviet P-6 boat, but as much as it pains me to do so ... I must agree with Mr. Ross. Doing something like that would take an awful lot of scratchbuilding and modifying to get something accurate.
BUT ... that said sir? Remember one thing; it is YOUR model and your time and skill and if you feel that you achieve it? DO IT and I'll applaud and support you every step of the way.
Recently, I had a model of a RN MGB built up from the AIRFIX RAF ASRL kit. The modeler CHOSE not to lengthen the kit's hull the 11/16ths of an inch to make it into a 70 foot hull. He did not do this after he looked at a few photos of the real MGB and at the kit's hull and deck. He did not think it'd be worth the trouble to do so. Do you know what guys? I agreed with him, when you look at the finished model and a photo of the real MGB, you are hard pressed to see a difference.
Unfortunately, he did forget to widen the cockpit area - that's the most glaring (at least in my opinion) error. But, in his defence, the photos we used did not show that area of the real boat to good advantage. I like having modelers use photos rather than drawings as drawings could be subject to change AFTER the subject was built and photos - well - you cannot dispute what is in a photo.
I was told that, even though it was a nice build and a cleanly done build - I was wrong in my choice of subject, that if I wanted to use THAT kit for that conversion of the kit - that I should have done another MGB. Hey ... ever since 1980, I have held a theory that the conversion that I had done recently COULD be done - and it was - and I love the finished model and I think it's darn-tooting close to the real boat ...
So, sir, if you'd like to do that conversion of those two kits and using those parts to accomplish it, ... GO FOR IT!
As a little boy, my parents gave me a kit of a Soviet torpedo boat ... and even though it has been lost down through the years, I do remember it looking like the drawing of a P-6 which Mr. Ross posted in this thread. It was molded in dark blue plastic and I remember (even at that young age) that the hull reminded me of an Elco 80 footer and the torpedo tubes looked as if the Russians took them off of one of their Lend-Leased provided Higgins ...
I wish I could remember what manufacturer produced it and all that, but I can't. I do remember that it was the size of the Revell PT-109 kit, that it was molded in dark blue and had an electric motor.
Garth