Yes you can pay the whole amount in 2017 and get the full deduction (if you have enough total deductions to itemized). That's what I do. In fact that's how some people do tax planning. Every other year they pay both payments to get a larger deduction that year and then the next year just pay 1/2.
So for one year you would actually have 3 payments you get to deduct.
The April 2017 payment (from last year) and both Dec 2017 and April 2018 (paid in Dec).
Then for 2018 you would only have the next Dec 2018 payment.
Then for 2019 you would get April 2019 and Dec/April and so on.
