In this case, I would definitely look elsewhere for a home loan. There are many lenders that could easily handle this transaction. Based on the scenario you presented, your best option would be taking one loan and having PMI. (PMI is not permanent and second mortgage products are not easy to get through underwriting in this market)

At the end of the day. I would much rather have one loan at 6.25% with Mortgage Insurance then 417k first at 5.75 and a 150k second mortgage at 11%+. Lock your interest rate up and take the safe route so you do not lose the house. Based on your credit/income and assuming your are in the 719k zip code, you would be approved easily for that loan.

One word of caution, make sure that this purchase is not in a declining market whereas you will need to put an extra 5% down.

Wells is pushing away from these new larger conforming standards, and instead wants to do a first at 417k and the balance after down payment on the second. As an update Wells is now saying they will not do the second in house and the Wells banker is going to look around for other banks. Credit score over 800, 200k plus annual income.
What are options in your opinion if the second does not get picked up?
Back end builder credits of $55k on HOA, Upgrades, Closing costs. Should I look elsewhere?