Thank you 'Glycerine' and 'BRobbins', I have been working with, and repairing vintage fountain pens for many years now, and I have large stocks of the feeds that you have illustrated in the picture above, what I was hoping was to find a company like Bock, who make a nib unit with the larger groove, and three 'slits' running down that 'trench', so that when the owner of the pen pushes the button rather vigorously, it doesn't burst the joint where the sack is fixed to the back end of the section. [And, yes 'Glycerine', I do use adhesive to stick the sac in place,] but I have found that modern pen users do not realise the amount of pressure that is caused when using a button filler, which of course wouldn't be a problem if the 'groove' was cut deeper, and wider, like we can see in the example shown 2 posts above this message!
Since writing about this, I have spoken to my good friend Graham, [who makes my base-pens for me] and he is going to find out if Bock do make or could make the type of nib units that have this type of 'groovy-trench'!!!
We shall wait and see!!!
Many thanks for your responses though.
Truffle Finder.
PS. I 'kinda' like this place! I take it from looking around here that 90% of you are from USA, I have just got back from the Columbus Pen Show in Ohio, I was demonstrating my craft at my stand during the weekend, and I gave a long talk about how my hobby progressed to what I do now as my 'living'. I only wished that I had delved into Google to see what was on there about myself [as I did last night because I was jet-lagged!] and found out about this association! If I had known about you before last weekend then I could have told you about me being there. Do many of you guys [and girls!] go to the American Pen Shows?