Offset bet, then reduce spread once one side is matched

[Fugazi]

So say I have an offset of 5 set.

Is there a setting whereby once either the back or lay is matched, it then changes the other bet to be within 3 ticks?

[Dallas]

If you mean offset bets at a different number of ticks/percent, then just split your opening staking into smaller bets, for example using a £10 you could place the following
£2.50 offset 5 ticks
£2.50 offset 8 ticks
£5.00 offset 15 ticks