I have to say Dont lock the front..

My TT01 Slides Great with a Blu tac locked rear end..

Thing is, if you lock the Front AND rear Diffs and have a highspeed Stack where the Drive is stopped at High rpm then the transmission shock is gonna be Mammouth and if you dont strip your diffs or Spur gear then the Prop shaft is gonna warp badly.

Leave the Front alone
If You have a High Speed Stack, then at least the Front wheels will be able to deal with the sudden stop and one of them will spin relieving the momentum from the transmission..

Just keep practicing.. Work on your technique..