I have some what of a spod fettish, and have about 40 of the little darlings. Without a doubt the best spods I have ever used are the grey ones from Fosters of Birmingham. They hold bait well (Dont over fill them) they have a wooden nose so are quite heavy and cast like a dream they also have enough holes in them, and just the right size so they skip over the water and have a superb retreve, a close second are the Korda jobies but the holes are just a little to big. The secret with any spod is to not over fill or push a pva nuget in the end. You could also try a ground bait plug to keep it in.
Best of luck
Jonathan.