This seems to boost upload speeds to Transmission to 16MB/s. It may require a corresponding amount of buffering in memory, that could require work later.
// Maximum pending requests we allow peers to send us. If peer requests are buffered on read, this
// instructs the amount of memory that might be used to cache pending writes. Assuming 512KiB
// (1<<19) cached for sending, for 16KiB (1<<14) chunks.
-const localClientReqq = 1 << 5
+const localClientReqq = 1024
// See the order given in Transmission's tr_peerMsgsNew.
func (cl *Client) sendInitialMessages(conn *PeerConn, torrent *Torrent) {