any advice/directions on removing a low level and fitting high level poiler on a blob
 

I have a 04 wrx and have now picked up an original sti high level spoiler in my paint code, so as it doesn't need painting I was planning on fitting it my self but from first glance the sti one has more bolt holes than the low level one currently fitted.
If anyone can advise on how to go about it pls as I don't really want to drill boot lid would using the current fixings suffice with the use of some sort of bonding agent?

Thanks in advance.