Ok, just a basic question, I'm rank 472, what rank should I instal my Radiant Surge Cannons?

Wait ill 500 for mark 5
600 is mark 6
700 mark 7
and so on .

I know, but isn't there a certain rank where the jump is very different and makes it more worth while?

The highest I've seen was Radiant VIII, so probably rank 800 ones are the max.

Hi
Size Attack Ratio

radiant Surge Cannon - Mark I 9 40 4.44 Rank 1 to Rank 99 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark II 12 60 5.00 Rank 100 to Rank 199 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark III 17 100 5.88 Rank 200 to Rank 299 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark IV 20 150 7.5 Rank 300 to Rank 399 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark V 24 200 8.33 Rank 400 to Rank 499 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark VI 30 300 10 Rank 500 to Rank 599 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark VII 36 400 11.11 Rank 600 to Rank 699 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark VIII 40 550 13.75 Rank 700 to Rank 799 and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

Radiant Surge Cannon - Mark IX 50 675 13.5 Rank 800 (and higher) and use a Radiant Surge Cannon Artifact 2 Radiant Weapons

so 700 to 799 is the best one? that's what I was asking, thanks

Yes ratio wise

....just don't worry about it... once you get high enough for Mk 9's the wasted deck space won't matter to you anymore... just go with the best