How would I split a string into substrings ending with a delimiter and a maximum length?

I have a list of parameters, formatted as a string of integers and reals in both simple and scientific notation, with a comma as delimiter. A short sample:

parameterString="126,10,3,1,0,0,0,0.0,0.0,0.0,0.0,0.4890289E+00,0.5741907E+00,0.6593526E+00,0.7445144E+00,0.8296763E+00,0.1000000E+01,0.1000000E+01,0.1000000E+01,0.1000000E+01," 

I need to break this into lines of at most 65 characters, where the last character has to be a space. The last non-space character has to be a delimiter, the rest will be padded with spaces. I would like fit as many parameters on a each line as possible. So far, I've found only a rather clumsy loop approach:

parameters=StringSplit[StringReplace[StringJoin@@parameterString,{" "->"","D"->"E"}],","] full={};count=1; While[count<=Length[parameters], s=""; While[count<=Length[parameters]&&StringLength[s]+StringLength[parameters[[count]]]+1<65, s=StringJoin[s,parameters[[count]],","];count++ ]; full=Append[full,s] ] blank=StringRepeat[" ",65]; full=full/.s_String:>StringReplacePart[blank,s,{1,StringLength[s]}]; 

It does the job, but I wonder if there is a more elegant solution to it, maybe a clever combination of StringSplit and StringPartition.

To put this into context: I am exporting splines in IGES, a standardized file format for CAD. I am aware that there are export formats available like DXF, but I never got them to work exactly as we need it.