Hi Thought a few links to documents from CASA might be handy for anyone contemplating a build. Kit or plans or even factory assisted build. These advisories are from 2000 ,however I believe they are still relevant.[ they were modified last month] The first one describes how to comply with the 51% rule. https://www.casa.gov.au/file/151991/download?token=oStoRPdy This one is more focused on the certification process https://www.casa.gov.au/file/151881/download?token=2uCN_Fie As both document refer to the FAA approved kits list ,here is a link to the List.....PDF last updated August 2016. https://www.faa.gov/aircraft/gen_av...uilt/kits/media/amateur_built_kit_listing.pdf If your kit is not on the FAA list then you should use the check list on the last pages of the top linked document. CASA may have a list of 51% approved kits. But I cant find them. Here is the FAA Amateur-Built Fabrication and assembly Checklist Job aid. As CASA is happy to accept kits approved by FAA it would seem relevant to use/read even if it has no legal standing in Australia. https://www.faa.gov/aircraft/gen_av/ultralights/amateur_built/kits/media/Am_Blt_Chklist_Job_Aid.pdf. It is important to meet th 51% rule so you can do your own maintenance ,either RAA , or VH experimental [after completing a course I believe] I will post more links to legislation and relevant material soon. Brendan.