You seem to be wanting to eliminate margin interest on a large covered call position. This indicates that the position is way, way too large for the account.

it's not (it's maybe 1% of my portfolio), but sure you can think that based on what I'm looking to do. I'm looking to overall mitigate margin carry costs on a stock I don't think is going to appreciate past the cost of carrying the stock on margin. I still want to be long the stock, but not pay ~0.75% x 30% of value/month to do so.

ie. I don't forsee this particular stock appreciating enough in the short term to cover the now higher margin carry costs.

Do not attempt if you are asking apprentice level questions

I'm aware of what the trade is, and the risks involved with a short straddle. Since half the people replying can't even figure out what the trade is trying to accomplish, (yourself included, apparently based on your reply) I wouldn't really consider this to be an apprentice level question.

I'm looking at specifically the buying power implications of moving from a share position to a synthetic share position, not the associated risks with doing so, I know that I'm potentially exposing myself to more upside risk on the short call in the event that the strike is breached. I'm willing to take that risk given it's unlikely to see a 50% appreciation in 10.5 months.