I know you have to add the 11 coil .40 spring to the G17 mags when adding the factory plus 2 extension.  

When adding the plus 2 to the G19 mags, should the G17 spring be added to the G19 mags when doing so?

Thanks!

Absolutely yes

Thanks, that's what I figured

I have never heard of this... and I have attended the Factory Armorer course a number of times.

I have seen more +2 magazines in use as a professional Firearms Instructor/Range master over a 30 year career than I can count.

I see no harm in using the longer springs... I also see no necessity in using them (unless the magazines have seen heavy use, a spring change is not needed)

# Do you have a source to link that Glock recommends the longer springs with the +2?

I believe it was on Glocks website under the magazine springs on the team glock store.  This is from Big Tex Outdoors and I don't know who wrote it:

"GLOCK Magazine Spring; 9mm, 10mm, .357, .40, .45 Auto (10-coil)

G17, G18, G34: all 17-rd mags, incl. pre-ban, LE-marked & current unmarked (std 10-coil spring)

G20: for all 15-rd mags, incl. pre-ban, LE-marked, and current unmarked

G21: use only in pre-ban, older LE-marked mags with 3955 follower & 10-rd mags

G22 through G35: pre-ban mags & older LE-marked mags (do not use with Tac-Lights)

We recommend this spring as an extra power mag spring for 15 round, 9mm mags and 13 round .40 and .357 magazines that are using the GLOCK +2."

With that being said my G19 +2's with 10 coil springs are extremely hard to get the 17th round in, 16 is good to go, 17 really tight if I can get it in.

I would rather just get the 17 magazine,with the cost of the +2 and the spring you could just pay $5-10 more and get a factory Glock mag.
I understand some people don’t like the way the mag sticks out but that doesn’t bother me anymore.

YES

in 30 years, you've never seen the need? That seems hard to believe considering my much more limited experience? I installed brand new factory +2 exts on 8 factory G17 mags. All of the mags were relatively new/low round count mags that functioned perfectly before adding the new bases. With the new bases installed using the original factory G17 springs, they all had random feeding issues. Installed XP springs and they all returned to 100% reliable.

So personally I don't really care what Glock may or may not say about it. IME... if you are going to installed extended base plates, install extended mags springs too.

This is the better option.  I still don’t completely trust a Glock +2 extension.  I have a couple pop off or crack when dropped or hit just right.

if your extension doesn’t come w one already, yes

The 17 rd mag offers the same and is built properly tho.

I just added a glock OEM +2 extension to a new gen 5 15 round mag.  Kept the stock spring in it.  It fed fine, but failed to lock back 80% of the time.

100% THIS......
My 30 years with Glocks and I absolutely agree.extend the follower travel...get the longer spring.. .COMMON SENSE.