Jason, thanks for the info, but, unfortunately, I have decided that I will not do this mod on my M45.
I have this bad habit of keeping my car keys in my pocket at work. Occasionally the keys get pressed unintentionally when my car is parked near my office desk and I sit down. In my old Q, the rear trunk release required a hold-down for a few seconds, so it never triggered accidentally, but I did have the occasional "panic button" presses!
On the M45, there is no delay on the trunk release button ... a few weeks ago, a colleague went out and was looking at my car and noted that the rear trunk was open (the usual slight lift) and pushed it closed. Clearly, when sitting down, I had inadvertently pressed the release!
If I had had the "open all the way" product you are talking about here, the trunk would have been open wide for quite a while. I guess I do not want that possibility to occur in the future.
I had once tried to get into the habit of taking my keys out of my pocket and putting them in my desk when I get to work, but after forgetting to take them with me downstairs (more often than I would like) and having to walk back upstairs for them, I kinda gave up that idea.