I'm new to DTH, just created an event with group registrations, and I can't collect a per-person deposit This is really frustrating!! I'm running the most current version 2.7.15. I agree with turbosatan. This really is a gaping hole. Developers?
Go to DT Register -> Configuration. At the bottom of the first tab, you can set how various fees/discounts are handled in group registrations and if they are applied for the entire group or per person.
In this case, set the partial payments to each member. Then the fixed deposit amount will be calculated and multiplied for each member. Or a minimum payment amount will reflect a minimum per person figure as well.