Scaling up a crumble?

[msrisotto]

Sorry, posted this in baking as well but received no responses so thought i'd try here too.

I'll be making this Rhubarb Crumble on Christmas day. I've made it once before, it's perfect. However i'll need to times the recipe by 3, to feed 11 people. To serve 4, it cooks for 30 minutes. I'll be using a bigger dish obviously, so I was wondering if I needed to increase the cooking time. What do you think? Also, i'll be using a fair proportion of defrosted Rhubarb, do you think that will make a difference? TIA

If the rhubarb was frozen already stewed, it shouldn't make a difference. I have a crumble recipe for 6-8 and it cooks for 40 mins on gas 4. I think the problem with cooking longer for a larger crumble might mean it burns on the top. I would be inclined to reduce the temperature part way through and do it a bit longer.

I could cover the top with foil for a bit so it doesn't burn.

i cook my crumble filling and topping separately to avoid the cold filling and burnt top scenario . i then assemble it together at the end.

Does the topping need long? I obviously could see if the filling is done because it'd be bubbling all the way through, but the topping ... does it just need browning a bit?

The topping didn't need long, about 25 minutes or so until it becomes golden brown. Once the filling and topping have cooked through just transfer the topping onto the filling and serve.