Tight-fit multi-channel ultra-high field (UHF, >7T) transceiver (TxRx) phased arrays improve transmit (Tx) efficiency in comparison to larger Tx-only arrays. However, tight-fit TxRx-arrays may require matching for each subject. To evaluate a potential use of tight-fit TxRx-arrays without matching, we investigated both numerically and experimentally an effect of a strong mismatch on performance of a 9.4T 8-channel human head TxRx-array. We demonstrated that mismatching caused only ~5% decrease of the B1+ field, while may have stronger effect on the maximum local SAR. Additionally it also effects the SNR distribution. While overmatching favors SNR, undermatching may enhance Tx-efficiency evaluated as B1+/√SAR10g.