Common opinion is not to mix brands - I even thought of mixing compounds front to back and was advised not to
The 48’s have a stiffer sidewall than the 888’s so I would have thought that alone would upset the balance
I ran mediums on the front and LTS on the rear for a while and it was OK**, it certainly turned in well when the front were new 
** I am a ham-fisted monkey
Checked in the half light this morning and couldn’t even see the yellow dot! Must have worn off from all the washing 
or be a sign of how old my tyres are (pushing 3 years, and 7.5K miles).
The Turini wheels with 888s in classifieds have me tempted, but I promised myself no more expenditure before the new year!
888’s because of this and have never looked back.
Right. Purchased a used set of wheels, and a part worn set of 888s, and stuck 'em on the car this afternoon.
Instant transformation! The car no longer tugs and pulls with undulations/ruts in the road, and high speed wheel wobble has been eliminated
Glad I read this thread, and thanks for the advice folks 
Used to pi55 me right off 
great tyre I’m sure but nevertheless…
Enjoy.
Not had wheel balance problems before
BUT
always use Adams and Page