As you discovered, you have to be careful about tilting it fore or aft. The pedal position, when centered is perfect, but when well forward or aft, by holding the pedals... the spine tilts. That can cause the forward or aft end to get below the lip in the hull.
If Mirage users are having difficulty fitting the MirageDrive into their kayak correctly, the following information can help to explain an easy process for fitting the drive. This is primarily a problem with new users and is possibly complicated by the Drive Seal accessory mounted at the back of the drive. Correctly Seated MirageDriveIssue:
The MirageDrive must be lowered into the drive well evenly front to back. Tipping the drive forward or aft when lowering can cause it to wedge into the well. Holding the pedals with adjustments far aft or forward causes a potential problem.MirageDrive Tipped Forward
This is sometimes caused by the added friction of the drive seal mounted at the aft end of the drive. In the worst case, the drive spine will miss the forward ledge and drop below the hull. Tipping the drive aft when this happens can then cause a compression and damage of the aft well wall. Pedaling the drive in this position can also damage the aft fin. Incorrectly inserted MirageDrive
Note friction caused by the Drive Seal Accessory
Correct installation of the MirageDrive: It may be easier if you place the pedals in a middle adjustment to help identify a "level" drive as it is lowered into the well.Lower the MirageDrive...level with the well
Another trick is to hold the drive at the base of the pedals from in front or behind them depending on the fore or aft adjustment.Hold pedals at or near drum center
The MirageDrive is quite simple to mount... when you understand how it fits. Friction caused by the Drive Seal accessory has caused a potential positioning challenge for users as this tips the drive forward. You may consider removal of the drive seal to make initial use of the drive easier. This makes mounting the drive into the hull easier for some users.
We added an alignment pin a couple of years ago to assist in dropping the drive in level. It now forces the drive level as you drop it in.
Problem is most common with the pedals adjusted well aft (for shorter pedalers) which tips the drive spine forward if holding by the pedal shafts.
I can't imagine a fin falling off in this manor by simply installing the drive. It takes considerable torque to pull the brass nut through the fin. May have been another cause or hanging loosely from a previous outing.
Fyi... Hobie Mirage Kayaks are coming with a drive alignment pin feature since 2012 model year to help prevent mis-aligned drive installation. Way easier now.