Hey Mark,
The short answer: no, we don't support custom fingerprints or customizing what TurboActivate, TurboFloat, and LimeLM use for the fingerprint of the computer. We have a proprietary algorithm which is very, very good at fingerprinting computers (very low false positives and false negatives).
The longer answer: Our fingerprinting algorithm is unique from competitors algorithms. We don't require a dongle to be able to uniquely identify computers. Nor do we need a dongle to limit running your app to a fixed number of computers (for example, on letting your app run on a single computer).
If the customer wants to move between computers using LimeLM there are a couple of choices:
1. Use TurboActivate and let the customer deactivate your app from a menu. See: http://wyday.com/limelm/help/activations/
2. Use TurboFloat (our concurrent licensing product) and the customer can just open your app and close them without worrying about deactivating first. See: http://wyday.com/limelm/help/using-turbofloat/
It sounds like with your example of how customers are currently using dongles that the first option will be best for you.
Would that be workable for you and your customers?