You can check the losses of various cable types using VK1OD's handy
Transmission Line Loss calculator here:http://vk1od.net/calc/tl/tllc.php
For example, the loss on 2m in 100' of Belden 9258 (RG-8X) is 3.8dB, so
about 42% of your power reaches the antenna. If a 50' piece will reach,
then the loss would be only 1.9dB, so 65% of your power is radiated.
Does it make a difference? Depends how much margin you have on the
radio path. Probably isn't detectable for local repeaters, while there may
be cases where it makes the difference between being able to pull your
signal out of the noise or not at the other end over marginal paths.
Summary: RG-8X works, but not as well as RG-213 (though it is more
flexible and easier to work with.) Longer lengths will have more losses
than shorter ones when the antenna is in a fixed location (but if the
longer length allows you to mount your antenna 30' higher in the air,
it is worth the added loss.) It all comes down to signal strength: when
signals are strong enough the loss doesn't matter. On weak signals it
may. There is no absolute answer.
One other point: coax loss or the type of 50 ohm coax will NOT damage
your radio. It simply affects the amount of power that is lost between
the radio and the antenna. The only time that affects the radio is when
you have to run it on high power all the time and it can get rather warm.
It will do that regardless of the type of cable, of course, but sometimes
a good enough antenna system will allow you to run it more often on low