Advice on wheel fitting

[RobClu]

Hi experts.
I'm looking for a bit of confirmation/correction on my plan, which is:
Merc SLK wheels 15 x 7J H2 with ET37
205/65R15 tyres to keep the rolling circumference similar
Front - 10mm spacers with conversion studs
Rear - seem to fit OK with or without 10mm spacers
Holes seem OK but not sure about seat shape.

Q: Is it daft to have spacers front and not rear?
Q: SLKs are fast but not heavy - any worries on weight? (can't find any weight pointers on the wheels)

thanks for any thoughts...

Rob