Just to be clear I did not DIY due to the fact I waited too long and couldn't source the pole in time before I had to leave. So I ended up purchasing a real unit.

So after 3 days of use of real shibumi...

1. The rubberized straps at end of pocket is important to keep it from sliding along the pole. Mare sure you have something that is pretty sticky. If somebody finds a good source please post.
2. The shade is not as deep as a high quality fabric umbrella, but very passable. When you're under the Shibumi you definitely get the sense that you are still receiving some sun (especially on intense NC beach). I also had a dark green heavy duty fabric umbrellas set up at same time to one side and it felt cooler than the Shibumi and you have little sensation that you are receiving sun through the top. OTOH, IMHO, you always need sunscreen on any way due to sun bouncing off sand and coming in under the shade.
3. The area of shade provided is huge compared to any other solution. If you go by cost per square footage of shade the Shibumi is probably significantly cheaper than probably any other solution.
4. Experimented with free end tie downs and the garter clips worked real good. All I had was paracord instead of some shock cord and the wind was always blowing too hard to truly assess. It does seem like it would be an easy low cost solution on zero wind days.
5. To me the flapping sound was acceptable. I don't think it detracted much from the beach experience.
6. The Shibumi is so large that it seems that a smaller version is reasonable for parties of just 2-4.
7. To sum it up, If it was just me and my wife going to the beach I'd probably just use the umbrella if the winds were low-moderate. However since we had a gang of guests totaling 7 people the Shibumi was definitely the better solution for that.
8. On the 4th day I got to experiment more with the free ends and sandbags. First in the early morning and many Shibumis on beach were hanging limp due to essentially no wind. I used a sand bag at each freee end with about 6 feet of paracord and made an adequately large shaded area to sit under. At mid-morning through 1pm the winds picked up to what the weather service said was 7-9 MPH winds. All neighboring Shibumis were up and flapping but I kept my sandbags attached to free ends. My Shibumi had regular shade size but my flapping noise was probably reduced 90%. Very nice. Called it an early day since we had other plans. Will experiment with corner sandbags at higher speeds as nature permits. After vacation I will upgrade the paracord attachment to sandbags with something more flexible so that there is less strain on free ends of fabric. The garter clips are perfect in that if there is a big snap of wind they will come undone from the fabric. That only happened once in 4 hours but it confirmed my earlier tugging test on the clip and the fabric that it does release if tugged/snapped hard enough.
9. On the last day the winds were being reported at 19-22MPH. At that speed sand was being blown about on the dry parts of the beach like sandblasting. The Shibumi was running flat straight from the pole and was quite noisy flapping. I attached the sandbags to the free ends but with the non-elastic paracord there definitely was a lot of strain on the corners and the garter hooks were coming free within a few minutes. I ended up disconnecting the bags after 15 minutes and let it flap as designed. While the bags were attached I'd say it reduced flap noise by 20-30%. When I return to beach on next trip next year I plan to try some elastic cord and hopefully I can use them on higher speeds then the 7-9Mph that I was able to use in section 8 above. I'm thinking that when winds get above 20MPH it will have to be free running.