That is a good guide though I have never seen or had to use the taping pin trick. There are a few other HF threads on flashing this card if you have problems.
You are also likely to find a better price on the 7 slot models and the 13 slot models were just released. Functionally the two versions appear identical, it all comes down to whether you require the two 2.5 hotswap drives on the outside.
Most of the systems on eBay seem to be the "TA"...
I have good experience with these HGST drives but they are quite slow. In my opinion a better option is the new Seagate NAS drives. The price difference for a 4TB Seagate is $200 vs. $150 for the HGST but the speed improvement (sequential read/write is very close to 7K4000 HGST drives) and...
Take a look at this post
Based on the example above, an 8 drive raidz2 vdev: 128K/(8-2)=21.3K = Bad alignment, not a multiple of 4K
In a 10 drive raidz2 vdev: 128K/(10-2)=128/8=16K