I am assembling a genome of size 120Mb from 5 different libraries of different inserts. Insert sizes are 300bp, 1Kb, 8Kbs, 20kbs and singletons. first two libraries are from Illumina genome analyzer(Read length: 76bp) and the last two are from HiSeq (Read length: 100bp). After reads trimming mean lengths are 55 and 87bp from GA and HiSeq runs. I want to do assemblies with velvet, would the k-mer size of 35, 45, 55, 65, 75 will crate any issue? Since my trimmed read length is quite varying? Will it be fine to assemble both GA and HiSeq reads together or should I assemble separately and merge assemblies later? I would appreciate the decent comments.