Do they have any weight and aerodynamic drag in simulation? E.g.: if I add an anemometer on a German plane, does it reduce aircraft top speed?

I believe that they do. According to the manual:

"Some field mods greatly improve your ability to manage the performance of your aircraft or your navigation efforts. Many weapon mods can give you increased firepower, but they can also come with a noticeable performance hit once installed. Choose your field mods and weapon mods wisely! Their added weight and drag is modeled."

RTFM, as usual! Yet I'm not a rookie! I should know these things!
Thanks Argon!

However, from some minimal experiment I have done, it seems that the speed reduction due to the gauges is nil and that due to the additional weapons very little. Here are my tests (all performed in Quick Mission at an height of 1 km - speed in km / h):

Albatros D.Va
Standard Payload = 171
Full instrumented = 171
Lewis overwing = 169

Nieuport 11
Standard Payload = 156
Full instrumented = 156
Two Lewis overwing = 153

Hello Greybeard - from my own experience, I would say that addition of extra instruments, speed indicators, etc., has no impact on performance or top speeds in RoF. Addition of extra guns, as evidenced by your numbers, does have some (slight) impact.

By the way, thank you for those excellent FMs for RB3D that you did many years ago - while I no longer fly RB3D, your tweaks were a major inspiration for my own FM/realism packs for First Eagles 2, as well as for the WoFF series. (A shame that the FMs are encrypted in RoF -- I'm sure that you would be able to do excellent things there, if the FMs were accessible, but it is what it is.)

Cheers,
Von S

Thanks for your kind words. RB3D was a magical period, which will not repeat itself. Forgive my presumption, but I too am convinced that I could do a lot with my experience for the RoF flight model, but they made different choices.
Nonetheless, I am appreciating the qualities of this simulator, continuing to discover day by day what for me are real refinements. It is not perfect, but it is the one I like the most among the ones I have purchased.

Ahh...RB3D...those were the days:
- Voodoo GPUs & Glide Wrappers
- Von Thom's Campaign Manager
- the Beery Super Patch
- Hells Angels Patch
- Full Canvas Jacket
...and your fine work of course

RB3D taught me a lot about PCs, modding, installing/uninstalling mods, etc. Probably because the stock game was so weak in the graphics/FM/DM departments. Sierra did deliver a fully interactive campaign and a nice manual - which I still have.

Red Baron II was great, I was so excited each time I read an article about its upcoming release. The original Red Baron "sim" from Dynamix was my go-to PC game for a number of years. Then when the 3dfx patch came out for RBII - I was living in sim nirvana with my Voodoo 2s in SLI.

I will say, other than FS-WWI, Rise of Flight is my go-to for "modern" WW1 simming. Granted, it came out in 2009 so it's quite dated. It still holds up very well for me. I of course have the WW1 add-ons for the IL-2:BOX series and it's great - just not as well fleshed out.

Agree - and if you use PWCG with all the available custom skins from Gooseh the overall effect is awesome.

fly the sopwith triplane with 1 gun and then the 2 gun option... youll notice a sever change in plane behaviour. Particularly in turning