XSLT split keeping a section static - xslt

Question

I am trying to split the file below to 3 items each and also keep the last section the same. Additionally, I also need to Header block that appears at the beginning with each split (except the last).
Input file
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<Root>
<List>
<Header>
<test1>a</test1>
</Header>
<Item>
<ItemNumber>
<Number>1</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>2</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>3</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>4</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>5</Number>
</ItemNumber>
</Item>
</List>
<List>
<EOF MaxMsgPerFile="3" >
</EOF>
</List>
</Root>
Here is what I have tried
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:variable name="tag">
<xsl:value-of select="/*/*/EOF/#MaxMsgPerFile"/>
</xsl:variable>
<xsl:template match="/Root">
<xsl:copy>
<xsl:for-each select="List[not (EOF)]/Item[position() mod $tag = 1]">
<List>
<xsl:copy-of select="Header"/>
<xsl:copy-of select=". | following-sibling::Item[position() < $tag]"/>
</List>
</xsl:for-each>
<xsl:copy-of select="List[EOF]"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
I get everything I wanted but I cant see the Header appearing at each split
Here is what is expected
<?xml version="1.0" encoding="UTF-8"?>
<Root>
<List>
<Header>
<test1>a</test1>
</Header>
<Item>
<ItemNumber>
<Number>1</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>2</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>3</Number>
</ItemNumber>
</Item>
</List>
<List>
<Header>
<test1>a</test1>
</Header>
<Item>
<ItemNumber>
<Number>4</Number>
</ItemNumber>
</Item>
<Item>
<ItemNumber>
<Number>5</Number>
</ItemNumber>
</Item>
</List>
<List>
<EOF MaxMsgPerFile="3">
</EOF>
</List>
</Root>
Any help is greatly appreciated
Thanks

Answer 1

How about:
XSLT 1.0
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="/Root">
<xsl:variable name="groupSize" select="List/EOF/#MaxMsgPerFile" />
<xsl:copy>
<xsl:for-each select="List/Item[position() mod $groupSize = 1]">
<List>
<xsl:copy-of select="../Header | . | following-sibling::Item[position() < $groupSize]"/>
</List>
</xsl:for-each>
<xsl:copy-of select="List[EOF]"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>