It's always best to bank on not being able to check it through. Then if you can - it's just a bonus. Some things help:
1. Being able to use First check-in (obviously you're a WP so you can, so this is a plus)
2. Being genuinely pleasant to staff
3. Telling them that you have done this before and that
your luggage has made it through and that, therefore, you're happy to deal with it if it doesn't work.
Of course if you're not happy to deal with it if it doesn't work, then don't request it to be checked-through. Instead, hope that the transfer desk are happy to arrange your baggage for you. It's always best to bank on not being able to have then arrange it for you. Then if you can - it's just a bonus. Some things help:
1. Having enough time for them to sort it out (you do, so this is a plus)
2. Being genuinely pleasant to staff
3. Telling them that you have done this before and that
your luggage has made it through and that, therefore, you're happy to deal with it if it doesn't work.
Fingers crossed for you!