A regulator can be tapped anywhere in the fuel system. Preferably after any sources of pressure drop along the way. The 4-way fitting at the fuel rail inlet tube is as close as we can get to the rails when re-using the stock rails. It works great... every 4-way fitting we ever made has sold (only 3 left in stock) and we have 100 more being finished up in the next week. We have countless customers running our S1.E fuel system (and legacy S1) over the last 4 years or so (which are based on that fitting) and it works great. About half of the fuel systems we sell use this configuration rather than replacing the rails.
I recommend waiting for the new batch to come if you decide to use one. The new one has the 6AN male top fitting machined directly into the part, making it almost .5" shorter than the last version with the thread-in fitting.
If you have any technical questions about it, feel free to post up or email us at
sales@cj-motorsports.com
I am excited to have the new ones ready to go, people will really like them.