Magene P515 PES Spider Powermeter

[ktryoji]

I'm not sure to understand what you mean.
I replaced an Ultegra crankset with a GRX 600, I didn't add any spacer and I don't see any play.
Beside, road cranks and "Gravel" ones are made for the same BB size.

Interesting, I guess the chain line difference is just cassette spacing then?

[ktryoji]

On one bike I have a GRX 810 FD with an Ultegra crankset and no issues.
The GRX FD has a wider range and can be easily adjusted.
I have an Ultegra FD with a GRX 600 crankset on anorher bike and it works more than reasonably well.
The only issue is that the chain slightly touches the FD while on the smallest sprockets and I couldn't get rid of it yet.

Now you make me really want to get one… For your other bike, was the grx fd clamped on or brazed?

[Fabilangson]

On AliEx (Magene shop) you can read:
Not Support T47-86.5mm and BB386 bottom bracket ！

On my Aliexpress product page is:
"Compatible with 68mm-86.5mm standard road bike bottom brackets."