We ended up doing exactly that - combining our Q1 and Q2 payments and putting them on line 1 of the tax payments worksheet. I could see that column 18a showing the estimated tax due for Q1 and Q2, but column 19a only showing the Q1 estimated tax payment. We put both payments into line 1 since they were both paid by 7/15, and that corrected the form, plus it did the correct excess payment carryover to column c.
