addRowData with jqGrid doesn't work correctly - jqgrid

Question

After I inserted a new row using
my_table.jqGrid('addRowData', selected_rowid+1, newRow, 'after', selected_rowid);
The new row is inserted correctly on the table but when I output the grid data
my_table.getGridParam('data')
the new row is inserted in the very end of the data array. Also, when I click any row after the new row inserted, the rowid was not updated (incremented).
Is there any way to fix this?
The grid definition is this:
my_table.jqGrid({
colNames:['Id', 'Start','End', 'Duration', 'Text','Position','Alignment','Warnings','Errors'],
colModel:[
{name:'rowid',index:'myrowid',hidden: true},
{name:'start',index:'startTime', width:10, formatter: convertTime},
{name:'end',index:'endTime', width:10, formatter: convertTime},
{name:'duration',index:'duration', width:10, formatter: getDuration},
{name:'data',index:'dataText', width:40, align:"middle", sortable:false, editable:true, edittype: 'text'},
{name:'position',index:'position', width:5,editable:true, sortable: false, edittype:'text'},
{name:'alignment',index:'alignment',width:5,editable:true, sortable: false,edittype:'text'},
{name:'warnings',index:'warnings',hidden: true, formatter: warnings},
{name:'errors',index:'errors',hidden: true, formatter: errors},
],
//pager: '#packagePager',
datatype: "local",
width: 700,
height: 800,
data: my.caption_data.rows,
localReader: {
id: "rowid",
repeatitems: true
},
rowNum: length,
viewrecords: true,
cellsubmit:'clientArray',
rownumbers:true,
hoverarrows: true,
multiselect: true,
cellEdit: false,
scrollrows : true,
multiboxonly:true,
autoencode:true,
});
I read a previous post and it seems like i can pass in "undefined" as the rowid. The problem is I want to have the ids sorted correctly. So if I insert a row after rowid of 7, the new row should have rowid of 8 and the rest should all be pushed back by one. Is this possible with jqGrid?