I know a few people who get calls off letters sure, but its still a vetting process to get to those most motivated. 

I am thinking about sending a carefully worded certified letter as my first attempt to contact them.  

You should have gotten a letter to contest the increase.

After doing this twice the HOA management will probably send you a “warning” letter.    

@Jamie Brayton i'd love to get in on the mixed gender meet ups in the capital region when they're happening!

This is why people don't like renting to friends/family because its human nature to mix emotion into the decision making and that makes dealing with managing the investment messy when things go sideways.

I recommend a formal letter with the bills attached and a deadline for payment.

I have started using a spreadsheet but I would like something that makes it easier to keep track of when I have sent the owners a letter or postcard etc; also to attach a picture of the property and some pdf's of county record documents.

We were able to overcome it by providing proof that we paid, and were completely responsible for the loan and had recorded documentation to prove it (letter to lender attached below -  (side note this was for a VA loan so we used an agreement for sale in this case). 

Adding interest rates to the mix makes penciling out deals increasingly tricky.