Not to pre-empt the issue but....
Flown an L-39, relatively benign handling qualities, but could still bite the unprepared.
Biggest worry with most of the Eastern jets is that they don't normally come with a manual worth a damn and few Western pilots or maintainers have had any experience of them. Often the manual is transalated from Czech via Russian and an African nation into pigeon ingleesh.
This means that unless the owner has gone to the expense of replacing the instruments with Western equivalents the cockpit can be quite unfamiliar and it can be difficult to pick up info in a hurry. God knows what it is like for the engineers!
Bad business,
Ghost