[HCRA] RJ11 mic extension - tech question

[kx1x at arrl.net]

OK.  I'll be the first to admit I'm not the most technical (electrical) person in the world.  Actually, not even close.   But, I do proceed under the assumption that there is no such thing as a stupid question, so here goes.

I have just installed a FT2800M in the car to replace the 'missing' FT1500.  The new rig is a little larger than the older one, but still fit in approximately the same place.  The problem is that the microphone cable is on the left side of the front of the rig, and pokes me in the knee.  I've been able to reposition the cable so that it is pulled behind the mounting bracket, and away from my knee, but I worry about two stress points that I've put on the cable:  1) at the RJ11 jack input, and 2) where the cable now circles around the mounting bracket.  At $60 for a new microphone, I'd like to remedy this situation before I have a problem down the line.  Here's the question:

Can I use a regular RJ11 (telephone) extension cable?  I understand that some of these cables are only wired with 4 wires, I would have to find one that actually has all 6 wires, and hopefully wires -- not the cheap copper foil stuff.  With this in mind, is there an electrical reason why this is not feasible?  I note that one of the leads has an +8v connection to the radio.

Thanx in advance for your answers,
'73 de Kx1x