Q re. unhardened shafting & linear bearings

Hi all

Recently had a small windfall and so can finally contemplate turning
ideas into hardware. Have been lurking here for a while and haven't
seen the info I seek discussed before, so here goes...

Am contemplating a machine that moves a load of about 4 kgs. (~10
lb.) at max velocity of ~4.5 m/min (though may go higher if
possible). Total length of travel is 3m (10'). Have some
*unhardened* (actually about 33C) 4140 20mm precision ground shafting
and linear bearings and support extrusion to suit. All enquiries to
supposedly knowledgeable persons (retailers of this stuff basically)
so far have resulted in what seemed to be uncertain answers.
Responses were
i) "Unhardened shafting is unsuitable since the hardened balls will
score the shafting" (No request for load, velocity, acceleration,
whatever made) or
ii) "I have never heard of this being done and have no pertinent
information available" = Don't know I guess.

So, has anyone here been as financially challenged as I am and toyed
with this situation. Or has sufficient theoretical knowledge to give
an informed answer.

If this isn't dismmissed out-of-hand and I actually try this setup
out will obviously post results here.

Alternatively, has anyone ever tried using bronze/teflon/graphite
impregnated/?? bushings as linear bearings? Have amps/motors with
extra 'grunt' if required.

TIA

Pete S.