Considering a miata...top modification questions

I'm currently in the market for a new car and the Miata seems to be a good choice for my desires: RWD, lightweight, inexpensive, and easy to modify. However, I am not a fan of convertibles (not that they do well in CO anyway), so I would have a hardtop installed full-time. I am curious as to a few potential modifications to the top itself, which is where my questions come in.

1. If I were to remove the factory soft top assembly, would I be left with a large gaping hole behind the seats that passes into the trunk? If so, is there a company that sells a replacement tray to cover this area?

2. Can the top be welded in place or permanently installed by other means, allowing for the clamps to be removed?

3. How strong is the factory hardtop? For example, if I were to put a 75-lb weight on top of the roof while it was installed on the car, would the top be able to support it, or would it buckle under the weight? I ask because I've been spoiled by the sunroof on my Acura and would be interested in installing one on the miata, if possible. I know, why install a sunroof on a hardtop miata when it's stock form is an open top? Well, I would be transplanting the audio system from my integ, and Denver has an unusually large amount of HU's stolen from vehicles every year. IMO a sunroof is the perfect compromise, even if it does raise the center of gravity slightly.

4. How is the liner installed on the hardtop? This applies to the sunroof idea as well. If anyone has a picture of the inside of their top and could post it I would greatly appreciate it.

Thanks for looking!