Dark strawberry/clip in platinum extensions

Hello Everyone

I have just joined the site, Hurray!!! I have been cruising in and out of hair boutique for a while now, I was actually reading through another forum and they recommended Hair boutique to each other, so here I am.

I have a question for all those experienced in clip in hair extensions.
I have dark strawberry blonde hair and would like to get some platinum blonde clip in hair extensions (a full set 20" 8-9 pcs) and get some platinum blonde highlights/foils through my natural hair at the roots so it doesn't look fake.

What I am thinking:

There is hardly anywhere you can get my hair color in clip in hair extensions so I have decided I am going to have to match the extensions some how. plus I have always wanted platinum blonde hair, but would never go down that path with my natural hair, in fear of frying my hair and breakage etc. I basically want the extensions to make change my hair colour temporarily.

Heres my questions:

My hair is approximately 19" long, I want 20" platinum blonde extensions I am not sure if clip in hair extensions cover your natural hair completely underneath or do they let your natural hair come through and blend with the extensions? If they do I figure my plan may work, what do you think?

Hope to hear from you all, great to be here!