Im looking for some advice on part orientation when gravity filling.

I have a sump Im casting and I am at the stage of designing the runner system.
The ideal orientation for this part (for ease of pattern making and runner system design) I feel would be to place the fins at the top.

Images below.

My concern is that with the fins at the top they will collect dross/slag and also not have a very high pressure for how thin they are.

Its a big part. 220mm high and 1m long. Mass is 16Kg aluminium - runner system.

Should I be concerned about this? Or could it not be a problem if I put some risers in there?

Bigger question. How would you do the runner system? Any advice much appropriated

This is my project if anyone is interested.

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