Internal cabling - covers?

[mayan42]

Hey,
newbie question, I'm building a frame with Di2 and hydraulic discs, with the aim of fitting both cables internally in the downtube.

I have covers for the Di2 holes, bottle boss reinforcements, with a 6mm hole.
For the disc hoses, i was planning on using these pictured, and not using internal guide tubes in the down tube. Looking at it now, i'm wondering how much support the cable cover will give to the hole i'm putting in the down tube.

I've had a look through the previous threads and all the examples i've found of internal cabling is using internal guide tubes.
I guess my question is, do i need to use internal guide tubes with these type of cable covers?

thanks