As Hartleelands said it is fishing its nuts off at the moment. Was in the vicinity this week fishing the Lage Vaart Canal and got my bait from Richie Woollard at De Koerberg camp site.
I am not too sure whether the Anglo Dutch Festival was fished in Hattem. Maybe just downstream near Zalk?? If you are fishing Hattem then we fish it every April for a week. Two methods are definately worth a look, Feeder as said before and also pole Feeder in my opinion. 35 turns is bang on for the feeder as it just about brings your bait back towards the crease (if you have a groin that is). If you do struggle to get bites then I have found that lengthening my hooklength to as long as 6ft has got me more bites on there. You need to be very regimented with your casting as well, only leave your feeder in for 60 seconds and recast. The river flows very hard and those casters dont stay too long!!!!
The big bream also sit in the slack water between the groins, although if you are pegged too close the the upstream end of the groin then it will be very ‘boily’ there so may not work as well.
Thats about it mate, just fish the river very positively. I do not think that you can overfeed the fish when fishing the feeder there. Most of your caster will be mopped up by Ide and Gusta (that is if the Gusta are showing!!)