Shimano 105 12 speed with 11-30 cassette?

[A.V.G]

Hello All,

Short version: Anybody successfully running Shimano 105 [Di2] 12 speed with a cassette smaller than 11-34?  If so, did you have to make any changes to the groupset in order to make it work?  Have you tried any other chains with this groupset?

Long version:
I'm spec'ing out my new aero build and have started collecting the bits.  For the groupset, I went with 105 Di2 and a Magene p505 52/36 crankset and I want to use an 11-30 cassette (by ZTTO). 

I've read and heard from various sources that 12spd 105 is designed to only work with 11-34 and 11-36 cassettes.  My question is, is this a REAL limitation of the 12spd [Di2?] groupset, or is this just Shimano's way of up-selling buyers into Ultegra? 

To further complicate things, I've purchased a [cheap] over-sized pulley wheel system. It seems to me that the difference between the Ultegra and 105 rear mechs is cage length - with 105 having the longer cage.  If my [cheap] OPS has a shorter-than-original 105 cage, can I get away with 105 & 11-30 cassette?

Bonus question: Since no part of the driveline (that touches the chain) is actually Shimano, is it worth trying a KMC chain? 

TIA for your input!

[Tilmanstoa5ty]

I'm personally running the standard 11-34 but i really don't see a reason why it shouldn't work. I think the only adjustment necessary is the b-screw everything else should be the same.

[PLA]

It works perfectly fine. Just adjust the b screw to match 11-30 spec.

[Super_davo]

I am running this exact set up on my 105 Di2 including the OSPW. Works fine but the OSPW is shorter than the original so I needed to remove two links from the chain else the tension wasn't enough in the smaller cogs on the inner ring (note that isn't an issue with the 11-30 specifically as the affected cogs are the same on 11-34 or even 36). Other (minor) annoyance that can't be fixed is that the e-tube app only allows 11-34 or 11-36 to be selected so when you're looking at stats, setting up sync shift etc. you need to be aware the real gear isn't what it says it is

[cycling-ms]

I ride the Ultegra Cassette for 10k km now. No problems!
For my chain I go for the Ultegra and dura ace chain, bc the china manufacturers like sunrace seem to have problems with 12s chains

[A.V.G]

I am running this exact set up on my 105 Di2 including the OSPW. ...

Thanks for this input.  I hadn't even thought about the e-tube issue, since this is my first foray into Di2.  Cheers