is there anything i need to keep in mind if i want to bottle from a keg at high volumes (4 vols)? the only thing i would think i need to do is increase the length of my hose, cold bottles and slow fill, am i missing anything?
I’m interested to see if anyone identifies an additional thing to consider when bottling such a high carb beer. From where I stand in my bottling experience - been using a Blichmann gun for 3 years - you nailed the ones I’d take into account: line length, bottle chill, and low enough pressure to the bottling apparatus (slow fill).
You could throw a stopper on the beer gun that is small enough to make it into a pseudo counter pressure filler, that may help limit foaming.
Use 15 ft of beer line. Get the line and Beergun cold too. I place mine in the freezer before I start.
And … only bottle in the winter in the cold garage. 
Although all ideas are good here, sometimes I bleed some of the pressure off of the keg when using the beer gun to reduce foaming. For the short amount of time that the pressure will be reduced, it won’t effect the carbonation of the beer significantly.
There are a lot of times when I bottle for competitions, I turn up the pressure on the keg a bit the day before to make sure that I can cap on foam. I then tuirn it back down after bottling and bleed off the extra pressure from the keg.
Just some additional thoughts.
Goose - That’s what I was thinking of when saying lower pressure to the bottling gun - - I pull the relief valve on the keg to have it under low pressure then dial my CO2 tank gauge to a relatively low pressure to fill slowly if I’m working with a highly carbonated beer. On the other hand, I find that with most beers I can dial the pressure I’m pushing beer with up fairly high (maybe 10 psi) with my Blichmann gun and not get unruly foaming so bottling goes faster.
High CO2 volume beer bottling 2.5-3.5+V?
Skip the Blichmann, way too much beer loss.
Only one way to go - counterpressure filling.
Williams-Warn, little pricey but works perfectly with scant beer loss.
Best new toy I have bought in years.