'maintain sufficient' is correct and usable in written English.
You can use it to mean to have enough or keep enough of something. For example, "We must maintain sufficient funds to complete the project."
Use of sufficiently large groups was, however, necessary to maintain sufficient statistical power.
His body could not maintain sufficient body fat.
Multi-walled carbon nanotubes (MWCNTs) were used as support to maintain sufficient electrical conductivity.
On Dec. 1, the company missed a $53.1 million bond interest payment, citing an effort to "maintain sufficient liquidity".
Those who used only a bottle failed to maintain sufficient stores of vitamin D and iron.
Single-ended one-sided read operations help maintain sufficient bitcell stability at 0.75 V.
Sodium/bicarbonate affected soils must be managed to maintain sufficient permeability to permit adequate leaching.
Legislation enacted in the late 1990s penalizes political parties for failing to maintain sufficient parity between male and female candidates.
Even before this controversy erupted, it had been an effort to maintain sufficient support for AIDS vaccine research and development.
Over the long run, how will the company maintain sufficient bargaining power and autonomy to guarantee good financial returns?
The completion of two courses per year is recommended in order to maintain sufficient academic progress in the certificate.
