Everything i read says 'Dont use crushed walnut!' Because of all the stories of the jagged pieces damaging their insides id never use it.
In my opinion its a risk im not willing to take but im glad its not been a prob for you F1 as i know your guy has been around a long long time =)
In my opinion its a risk im not willing to take but im glad its not been a prob for you F1 as i know your guy has been around a long long time =)