This is what I did for a marmalade IPA
20l Batch, 6.6% ABV, 51 IBU
4.5Kg Maris Otter
0.5Kg Wheat Malt
0.3Kg Crystal 150
25g Admiral 31.9 IBU boil 60 minutes
20g Mandarina 11.1 IBU boil 15 minutes
500g Marmalade boil 15 minutes
100g Lactose boil 15 minutes
30g Manadarina 8.3 IBU steep 15 minutes...