[Nefasine]

So on a whim by another player, I went and worked out the highest possible matrix defense a single device could have in shadowrun 5e

Firstly a note: I have excluded the Exceptional Entity Quality for any calculations as it basically allows an infinite characteristic if the karma is available (if I'm reading it correctly)

Willpower:
Pixie: 8 (8 )
Exceptional Attribute Willpower: +1 (9)
Custom drug = Tank base + Level 3 Stonewall: +4 (13)
Cybersingularity seeker (4 Limbs): +2 (15)

Firewall:
Fairlight Paladin: 9
Overclocker Firewall: +1 (10)
Modified Firewall attribute: +1 (11)
Home Device for Willpower 6 Metasapient AI: +3 (14)
Infusion of Firewall (Level 14 Complex Form): +14 (28)
ComPac-Esprit General PI-Tac: +6 (34)
Encryption Program: +1 (35)

Full Matrix Defence: Willpower+Willpower+Firewall (15+15+35)
=65

Notes:
I didnt count the PI-Tac and program bonus as 'Normal bonus' for purposes of Infusion of Firewall but if you do:
Infusion of Firewall (level 21 Complex form) +21
Firewall 42
Matrix defense = 72
This would require a resonance 11 Technomancer to score 21 hits on the complex form then survive the 22 physical Fading

[Zweiblumen]

TM would be better of Pushing the limit and Forming it a level 1. 

[Tym Jalynsfein]

TM would be better of Pushing the limit and Forming it a level 1. 

Not really, because the Level MUST at a minimum be EQUAL or greater than the Target Attribute. So if your Attribute you wish to Push into the Stratosphere STARTS at a 21, then you MUST have a Level 21 (or Higher) Complex Form for it to have ANY effect. 

[Zweiblumen]

TM would be better of Pushing the limit and Forming it a level 1. 

Not really, because the Level MUST at a minimum be EQUAL or greater than the Target Attribute. So if your Attribute you wish to Push into the Stratosphere STARTS at a 21, then you MUST have a Level 21 (or Higher) Complex Form for it to have ANY effect. 

Good catch (I was thinking of Diffusion).  And the editing in the blurb is on par... spell/complex form, what's the difference?  At least it has parity with the spell Increase [Attribute] except for Drain vs. Fade.

[Nefasine]

The Technomancer would need some prep or use of edge anyway;
21 hits means on an average roll the technomancer would need a dice pool of 63
now this is not impossible, especially if the technomancer is the required resonance 11 (320 Karma if starting at 6 btw)
Straightaway we can account for 11 dice from resonance
software of 8 is not unreasonable for that level of technomancer
then all is needed is 4 registered level 11 sprites
-this is a little harder as he needs a dice pool of 25 ((sprite level x 2) +3); 11 from resonance,  a skill and specialty of 14 (another 114 karma, if starting at 6 and specialty), using edge is easier

with out the technomancer support the dice pools are down to 51, which is still quite respectable