Our patio space, shown in the photo above, now is about 16 ft long x 8 feet wide with a ceiling height of 15 feet in our newly purchased condo, occupies the top floor (3rd) of an ocean facing building.

Not many options for antennas, and using Hamstick type antennas was my last resort. I wanted a full wave vertical loop for 20m but the coils then had to be very long which exceeded the 30% rule (ie-do not make the coils longer than 30% of the wire antenna length).
 
Yes, I tried stretching it to 50% and it did not work out as I was merely talking to myself most of the time!
An easy fix for me was cutting out some wire (oh, I used white colored wire for the entire antenna to match the patio paint!) on the coils to arrive at 3/4 wavelength and re-stretching the antenna.

I now have a square, or almost square loop measuring 13' horizontal x 12' vertical and a 2 foot long coil #14 wire (wound on 1" scrap PVC pipe) in each of the vertical radiators.
Using the formula, 1005 divided by frequency we arrive at 53 feet for a 3/4 wavelength antenna set for 14.250 MHz (1005 div. by 14.250=70.5 feet times .75=53 feet). 13' x2 plus 12'x2=50', and allow 3 feet for the 2 coils (I used 2 feet/coil). I used an air choke (6-8 wraps coax on 6 inch dia.) at the feed point to eliminate stray RFI especially out of the neighbor's TV set!
It is shown in the photo below.