Pete,
As mentioned above, overhead reels for casting need some sort of magnetic brake to make them user friendly. I remember using a Penn JigMaster in my Wellington days and enduring many a catastrophic birds nest until I learnt to thumb the spool correctly. It is possible to custom Mag a reel, that isn't specifically designed for casting. I'd suggest you look at two YouTube channels which cover a lot of this. One is Paul Edwards "Sandmans Tackle Time" channel or try "Pimp my Reel". In one video Paul has mag'd a Daiwa lever drag reel and it casts like a demon. I think the kits are available ex UK.