I don't think either approach is particularly good. The legs of a G5RV, like a dipole, are cut to a specific length for a reason. If you adjust the length you will have a fine antenna, but it will be optimized for a freqency outside the ham bands.
The G5RV design is actually 1.5 X lambda which makes it longer than a dipole. If you don't have the space for a G5RV why not just build (or buy) a dipole that is cut properly for the band(s) you want to work?
Finally, you might want to play around with some of the free antenna software. I like MMANA which is freeware from this link:http://www.qsl.net/mmhamsoft/
The software comes with a big library of antennas, so you can probably find a model for the antenna you are interested in. Then look at the radiation patterns from the standard antenna model, and compare it with the modifications you suggest to see what effects those will have. It is quite instructive as a learning exercise.