Hi @Barbara ,
Did you read my recent contribution VRM PV forecast (improvement appreciated) - Comparison Victron's Solcast vs. native Solcast - #16 ?
My analysis clearly shows that you potentially add and modify the data too much.
The solar forecast from VRM is simply not reliable anymore after modifications.
I deal a lot with weather forecasts both professionally and privately, so I am aware of the complexity. A decisive factor is how detailed and regional the weather data is. What I am always impressed by is how well and quickly DESS reacts to changing forecasts. I also have several weather reports and forecast programs running here in parallel. Some of them are from the paid professional sector. The VRM forecast is actually very, very good.