Diagonal cowl struts

[AJ88V]

The literature for the Powerflow exhaust system lists "diagonal cowl struts" for the M20C in their price list.

The picture from the PF slicksheet https://drive.google.com/file/d/1Zf-ZUKcKEpiImtYXfgiWbVMn2vkPnDFO/view shows what appears to be a rod extending from the firewall down to the lower front of the cowl.  The price list has them at an incredibly low $200. (incredibly low for anything bolted to an airplane! )

My cowl sags when I remove the top and side covers.  I only unfasten the top and halfway down each side of the side covers when removing the top and leave the rest connected to support the cowl front.  When removing the sides, I first partially reinstall the side covers to realign the cowl front before installing the top. (pro tip:  When installing the side covers, always start from the centers of the sides and work the fasteners out to the corners last.  This will let you move the lower cowl and sides more easily as you put together the whole assembly top included.)

Seems like these struts from Powerflow would be a good addition generally (although maybe they make access more difficult to other items in the engine bay).  Suspect they are included in the PF exhaust STC and they're not sold separately, but maybe this is also a J-model Mooney part that could be added easily to an old C model?

Anybody have them?  What's your opinion?

[Brian2034]

In the link you provided

Are you asking about the picture of the pilot side and that Diagonal brace?
 

[Brian2034]

3 minutes ago, Brian2034 said:

In the link you provided

Are you asking about the picture of the pilot side and that diagonal brace?
 

If so it’s a factory Mooney brace as far as I know.

Its on my 63 M20 on both sides 

[Vance Harral]

Those diagonal braces are factory parts installed on early-year-model M20B/C/D/E/Fs, but not later year models.  You can see this in the progression of the parts manuals.  Parts manual 202 for the 1961-1964 M20B/C/D/E shows the braces for the B/C/D on p. 106 and for the E on p. 111; and there are no applicability notes, i.e. all airplanes in those year groups have them.  Parts manual 203 for the 1965-1967 C/D/E/F shows the braces for the 1965 models on p. 165 and the 1966-67 models on p. 170; but there are per-serial-number applicability notes, which indicate not all airplanes had them.  Parts manual 205 for the 1968-1976 models do not show the braces in any diagram and make no mention of them in the parts list.

It seems clear that at some point the factory decided the braces were unnecessary and/or caused more problems than they solved, but I do not know why.  Our 1976 M20F does not have the braces, but the cowl still has the attach points for them.  So every once in a while, some mechanic understandably tries to tell us ours are "missing", and I have to dig out the parts manuals and show them how the factory stopped installing them some time in the 1966-67 time frame.

My guess is that Powerflow lists the braces as separate options because they are only supposed to be installed on the earliest year models.  If you don't have them, I'm guessing you have a later year model airplane.  If you feel they'd be beneficial to you and you want to be "legit", there is probably some legal way to install them using the earlier year models as the basis for approval.  But I'll leave that to the actual A&Ps to comment on.