Sorry Yves, missed your reply!
In answer to your question, I think the individual custom fields should go into this new box if you select the position for a field. That way you can mix it up if you choose. I guess when you select the position for this new box, that is when the box itself is shown - if no custom fields for this new position are selected, then the box is hidden. Please drop me an email with costs, so I can make a decision on whether to speed this option up.
Also, there is something else I'm thinking of for some custom work. At this stage need to know if possible and then can talk about the finer detail and costs. Would like the Organiser area of Matukio to link with the Joomla users table more. I'm starting to capture a variety of custom fields for my users that contain more information about them (we are a cycling site, so capture things like fitness, age range, average distances, etc...) all of this is captured during registration or when a user updates their profile. I use another extension to capture this - but all that does (from what I can see) is store the additional entries into another table and links back to users via the user ID. I'm looking to bring all the information out into Matukio, so when someone clicks on the link to see all about the Organiser, it shows this information. I guess you already have a link to the Joomla users table as you use the email address, so in my simple mind it sounds really simple!
Please let me know what you think - maybe drop me an email?
Cheers Pete