Dataflow circuits promise to overcome the scheduling limitations of standard HLS solutions. However, their performance suffers due to timing overheads caused by their handshake communication protocol. Current pipelining solutions fail to account for logic optimizations that occur during FPGA synthesis, thus producing over-conservative results. In this work, we develop an FPGA mapping-aware timing regulation technique for dataflow circuits; it relies on FPGA synthesis information to identify the circuit's critical path and optimize it through register placement. Our dataflow circuits Pareto-dominate state-of-the-art solutions, with up to 29% and 21% execution time and area reduction, respectively.