The new Digital Video Broadcasting Satellite (DVBS2) standard is able to provide capacity gains of about 30% over the previous standard by using a powerfull Forward Error Correction (FEC) scheme based on very large LDPC codewords and BCH codes. The implementation of the DVB-S2 FEC decoder is a big challenge. The designer must deal with the overall design complexity and the decoding throughput in order to obtain a high decoding performance in terms of bit error rate (BER). We present in detail a complete design flow allowing a better understanding of the algorithm in terms of complexity, performance and its hardware implementation. We focus on complexity-performance trade-offs due to message quantizations and we compare its effects on several algorithm corrections used to check nodes for DVB-S2 decoding. The simulation results show that the best compromise between complexity and performance is obtained for the FOMS algorithm approximation.