I've been putting off fitting my wooden dashboard upgrade for ages (read: months) because I've been umming and aahing over the finer details of installing speakers in the vent holes. I know that there are pros and cons, and highly conflicting opinions of doing this, but for reasons I won't bore you with here, my vent holes were welded up long ago, so it's a bit of a no brainer (in fact really it's the only practical option!). I've read many forum posts and articles, here and elsewhere, but I'm still missing the answers to a few questions:
Size - I'm aware the vent hole is 9cm in diameter, but the popular choice speaker size is 10cm. I imagine in a 10cm speaker that the actual cone is slightly smaller so won't foul the vent hole - or should I consider putting spacers in to avoid this? I intend to mount the speaker behind the dash rather than sink it in from the front so I won't have any clearance problems that way.
Fitting - as I'll be screwing the speakers into the wood at the back of the dash, I want to avoid the screws protruding through the front any - I'm sure there are horror stories of this - but what screw size/type are best for this? I'm aware that I'll still want the speaker to be pretty secure. OR (and this idea gives me the horrors slightly) would you recommend drilling holes through the entire dash and then using the same holes to mount the grilles with long screws all the way through? The only other option I can think of for the grilles is glue and I can see that having the potential to be untidy... or I could just leave them without grilles, although that in itself is risky...
Do I need to consider boxing off behind the speakers or are they fine open-backed into the dash void? I'm no expert on this but I'd imagine closing it off will give a "tighter" sound. If so, what can I use for this? Is there anything on the market or will I need to fabricate something (something else to rattle no doubt...)
Any other pitfalls I should consider/be aware of? And any speaker recommendations?
Thanks in advance!