I agree with Gary N4AST: the direct answer to your question is:

* Use the shortest length of good quality coax you can get away with.
* Use a good quality 1:1 current (choke) balun at the ladderline/coax
junction.
* If you find the tuner can't reach a match on some bands, only then
consider a 4:1 balun; even so choose a 4:1 **current** balun.

On the topic of G5RVs, some (unscrupulous) antenna suppliers provide a
nice long length of RG58 as part of the package to "tame" the VSWRs.
Take a look at some of the losses that introduces:
http://www.karinya.net/g3txq/g5rv/

73,
Steve G3TXQ