You also need to make sure that the outbound is a "one-way" fare basis. If it's a return fare bases (which most international all) then once you cancel the return, they will re-price the entire trip. The V fare will no longer be valid (as it's no longer a return trip), so the outbound will jump up to the cheapest one-way fare basis, which will potentially eat up much of the refund that's due.

If you're just changing the date this ins't an issue - but you explicitly mention refundable which implied canceling it...