So long as your runs are short, there should be no problem. I assume
your HT expects to see something reasonably close to a 50 ohm load, and
using 50 ohm coax for your connections makes perfect sense in that
case. Small coax in general has higher loss than large coax. For a
100 foot run, that might be a problem. For RG-174-type cable at about
25dB per 100 feet at 450MHz, 100 feet would be pretty awful. But four
feet is about 1dB, which you might notice but would be a fraction of
the contribution of, say, 100 feet of RG-8-type cable at maybe 4dB.
So, how long a "skinny cable" are you thinking of, and how long is your
RG-8 run in comparison?

Cheers,
Tom