The way I went about it was clamping it together and stuffing fibreglass inside the lip and mould it inside the upper curve where the crack is to strengthen it up again and fibreglass fillers on outside sand it down when dry takes about half hour to harden depending how you mix it then ordinary fillers sand smooth , primer then stopper any wee holes primer again sand. It's honestly not that hard just fiddly getting the fibreglass inside and moulded use a good bit of resin give it some more strength. Hope that makes sense 👍🏻