Hello Customer (name blocked for privacy) and welcome to JustAnswer!
Vinyl siding will not close this area unless, as you say, there's something to cover the soffit area. It can be made without closing the soffit but in my opinion it would help only when you wanted to save materials and you don't seem to have such a problem.
Also, if you need any ventilation then you can put vents on the soffit boards anyway, which is again completely your choice.
If you make him close the soffit with wood, vynil or aluminium you are not doing anything wrong.
If he needs help with the soffit, here's a do-it-yourself website with a page dedicated to garage siding and soffit:
http://www.doityourself.com/stry/buildgaragesiding
Hope this helps,
Have a great weekend!
Edited by designer16tr on September 15 2006 at 8:26 AM
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