Tech Levels and Quality on the SGII end

All this talk of differing technology  has me thinking (once again)
about how to run a SGII Campaign set in the FADING SUNS
universe.

"Note on the background for those who do not know it."

It is the dawn of the sixth millennium and the skies are darkening, 
for the suns themselves are fading. Humans reached the stars long 
, building a Republic of high technology and universal emancipation 
- and then squandered it, fought over it, and finally lost it. A new 
Dark Age has descended on humanity, for the greatest of civilizations 
has fallen and even the stars die. Now, feudal lords rules the Known 
Worlds, vying for power with fanatic priests and scheming guilds. 
Nobles...priests...aliens...knights...starships...psychics...lost
worlds...
ancient artifacts...FADING SUNS

So how does one bring medieval and Traveller Tech level 20 on the
same table keep it realistic and yet give the pikes and long bows at 
least a very slight chance?

If no one else knows, don't feel bad I've been at it off and on  for
four years without success.......)

The only reason to even try is that it will look colorful.....)

Don