After our first flight we resolved to fix the tail wheel lock. On the ground directional stability seemed poor and would be helped by the lock during take off and the landing roll. The lock was not engaging as it was misaligned. Shims of pretty poor quality were replaced and the lock realigned with the hole on the support tube. The bolts holding the tail wheel assembly would benefit from being fractionally longer to allow a full set of washers but discover sourcing metric bolts quite a challenge. I have ordered some Imperial and a reamer, will need to talk to licensed maintenance before proceeding.