"not yet optimal" is correct and usable in written English, and it is typically used to indicate that something is not yet as good as it could be.
For example, "The new marketing plan is not yet optimal, so we should refine it further before launching it."
The spraying behaviour of these powders and the wear resistance of the coatings that are sprayed with them are not yet optimal.
Although piglets have been born from frozen sex-sorted boar sperm, freezing and processing protocols in combination with sex-sorted sperm are not yet optimal for routine use.
If outcomes are to improve for children with medical conditions for which prevention or treatment is not yet optimal, it is critical that researchers who are knowledgeable in how to deal with the difficulties conduct pediatric studies.
The dictionary D0 helps minimizing the reconstruction error, and it is not yet optimal.
We attribute this to a not yet optimal determination of the time-dependent scale values of the VFM instrument on Swarm Charlie.
However, it could also be seen that the actual usage of the available information at the destination was not yet optimal as the results indicated a performance gap compared to adaptive relaying schemes in which only correct relays forward to the destination.
The elevated abdominal background points to a lipophilicity of [18 F]12 not yet being optimal, although the HPLC capacity factor (k' value) of the non-radioactive reference compound 6 indicated that.
This shows that available prediction tools are not yet fully optimal.
For high-risk endometrial cancer, we have not yet achieved optimal outcomes with currently available therapies [ 14].
Murphy et al. observed that some women became pregnant faster than expected after discontinuing contraception or instituting lifestyle changes and thus had not yet achieved optimal control or changed medications.
One of the main problems faced when applying EPCs clinically is that there is not yet an optimal culturing system that amplifies these cells in vitro for a long time while still maintains their precursor status.
