Jumpers - how long is long enough

This question relates to the jumpers found on speakers with Bi-wire terminals

Most people agree that most of the jumpers provided should be replaced.

But how long should the new jumpers be?

A fellow audiophile who has spent some time investigating this recommends at least 50 cm
- he also recommends the neutral be of a larger gauge and 70cm in length

I have no reason to doubt his observations, because he is extremely thorough with his research and I have also found his observations to be beneficial..

I was just wondering if anyone else had similar findings they would like to share on this topic

Regards - Steve
Forgot to mention that the two wires were separated by lots of space - they were not twisted or joined together.

So it seems that the consensus so far is... 
- the length of wires used for jumpers can have some impact on sound quality, depending on speaker type & design and the wire used. 
- It may be prudent for those people that are using jumpers on their bi-wire speakers to try different lengths of wire to see what sounds best on their speakers
- Direction of the wire can affect sound quality

Many Thanks for the feedback - keep it coming

The jumpers that I use for my JBL 4319s are about 7", tip of spade to tip of spade, or about 17.78cm., and they work fine, and better than the stock jumpers.

All then best,
Any thoughts on solid vs stranded?

A while back I used some fairly sturdy copper foil.

I haven't done this for a long time because I bi-wire most of the time.
I prefer the sound of solid over stranded in my cabling. If you liked the sound of the sturdy copper foil, then stay with solid.

All the best,
Well my experience has been 
Every time I tried to jumper
She said it wasn't long enough
Which is such a bummer...