I needed one of these on my old car because the rears barely had any braking force....always a bit iffy during an MOT. I didn't really notice and braking issues on the road or track though.
Probably best doing the adjustment on some brake rollers.
Where a vehicle has been extensively modified or converted, certain
Reasons for Rejection, such as for components ‘missing where fitted as
standard’ should not be applied, for example:
a car converted for rally use (i.e. rear seats removed and fitted
with a roll cage and full harness seat belts etc.) may have been
converted so as not to require a brake servo, power steering or
a car converted to a stretch limousine may no longer be fitted
with curtain airbags or functional Electronic Stability Control.
The answer to this query therefore depends on whether this track based car
has been extensively modified as above, or simply had components removed on
a whim and a fancy.'
A 70/30 front/rear split setup should be ok. Unless you're tracking it every week and reducing lap times you probably wouldn't need to re adjust it.
From the factory cars don't have perfectly equal braking force so you'd not notice it on a 15+ year old car.
I remember years ago lowering an Xr2i and not knowing to adjust the brake bias valve.
The car thinks it's got 3 fat chicks in the back and locks the rear wheels under heavy braking.