Cashing in AVIOS miles for J flight.
My dilemma, no J class is available, only Y. J only opens up about a week before flight time, but this date would occur after April 28th devaluation. This is a partner flight on JAL using AVIOS so full AVIOS, no off peak redemption.

So what is my best option?
1) Book a J seat for March 30th, (the furthest out that is available) and then keep moving my seat date forward until I get to my actual travel date beginning of June. So I would probably have to do this eight times?

Is there a cost to do this? Can I do this on-line without a phone call?

2) Book the available Y seat for the actual travel date at the beginning of June. Then when J opens up, upgrade Y AVIOS seat to J AVIOS seat.

Is there a cost to do this? Can I do this on-line without a phone call? Assume I would still have to pay the new J AVIOS redemption. So, any advantage to doing this?
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Until the devaluation, my plan was to cash in the AVIOS a couple of days before the flight date as there were always plenty of Coach seats available on every flight and 5 out of 7 days would have Business seats available as well. Our dates were flexible so if we had to leave a day or two before/after it was fine.