Tax Penalty Abatement

The IRS charged our small business a $10,000 penalty for late filing of Form 5472. We filed this form along with our 2014 tax return because one of our partners (>25%) is a foreigner, and he was related party in a $2,133 transaction. We submitted the filing 10 days late. Upon receipt of the penalty, we filed an abatement request, arguing that: the 10-day delay was the unintended result of the fact that this was the first time we filed this form; the Form 5472 instructions mention the penalty for failing to file, or filing a substantially incomplete form, but does not mention late filing; this is our company’s first offense, and this is the first abatement request we filed. The IRS denied the abatement request. Along with the usual arguments, the letter stated that we were subject to similar penalties in the past, even though that is absolutely not the case. I am interested in advise from anyone with experience in this matter, and, in particular, advise to strengthen our legal arguments.