Hi Randy,
From observation of flights and from prior discussion with you I realize that the Merlin PA 40 is a powerful engine but you also made the point about the engines flexibility. You told me some folks use it in modern full size stunters so there is plenty of controlled power. I have also seen the VSC reports of the Merlin 40 doing well in smaller classic size planes so there is the flexibility confirmed. Many of the Nostalgia era planes used Supertigre 46's and the 40 ultra lite weighs a little less, so it would seem that the more powerful Merlin is an ideal drop in more powerful replacement engine for many 46 size Nostalgia designs. I am surprised we haven't seen more reports on Merlins in Nostalgia planes but this class is still new and growing. Randy you probably have examples of customers using Merlins in Nostalgia that we missed or maybe there's a concensus of folks that just choose a PA 40-61 for these larger Nostalgia designs.

Those planes typically ranged from 610 square inches to 700 square inches but many of them listed their weight in articles in a range from 50 to 56 ounces+ but less than 60 ounces. Props were typically 11 to 12" in diameter and usually a 6" pitch but some used a 5" or some in between pitch. I clocked lap times for many of these designs at 5.3 -5.5 seconds on lines (eyelet to eyelet)of 63 ft. to max length (center of handle to center of plane) of 70ft.

So if someone was considering using a Merlin 40 UL for a Nostalgia design it raises some questions:

What is the upper limit of size and weight of plane you would reccomend A. while using a pipe?____ and B. while using a muffler?___ 

What props would you reccomend using with the Merlin 40 on these Nostalgia designs to acheive solid stunt runs at similar lap times while flying a Nostalgia design A. using a pipe?____ B. using a muffler?_____ What prop changes (if any) would you make for varying conditions?  I realize that your reccomendations are only a starting point and a flyer must experiment to find what suits them best.

I had started out with the idea of a Stiletto 660 with a PA Merlin 40 UL for power and then it occured to me that I haven't seen a post on using the Merlin as power for Nostalgia designs so I thought I would bring it up for discussion.
 
                                Thanks Randy,
                                                        Pat Robinson