Although there are a number of steps to making structural repairs, the process is very DIY-friendly. After cleaning the area with acetone solvent, smooth out the damage with a sander and coarse sandpaper, and then wipe again with acetone. Next, expand the area with the sander until achieving a 12-to-1 slope down to the deepest point, taking care to remove any sharp edges. Once again, remove dust with acetone. Cover the surrounding area with masking tape and paper.

Measure the repair site, and then cut six pieces of fibreglass cloth to size. Liberally apply a mixture of resin and catalyst to the site and, after a minute, adhere the smaller pieces of fibreglass cloth to the deeper points of the excavation, adding a coat of resin mixture on top. Roll out any air bubbles with a fibreglass roller. Continue applying the remaining layers of cloth in this manner. Once the final coat begins to gel, apply one additional layer of resin mixture, and let cure overnight.

The next day, wipe the repair area with acetone, lightly sand, and then wipe again. The process for finishing depends on the type desired. Most people choose one-part paint due to its relatively simple application; although gel-coat is more complicated, proper sanding and buffing can disguise application errors more than one-part paint. The final process, two-part paint, is expensive, difficult, and often unsafe for undertaking at home.

First link didn't work so I deleted.

www.boatus.com/boattech/casey/fiberglass-repair.asp

I hope these links help you work out which way you are going to repair - boat hulls are no different to your Dove camper roof.

Where are you located? There may be a small f/glass manufacturer that could do your repair with a chopper-gun for a reasonable if you did all the preparations - they buy the glass and resin at a fraction of the price that you will be able to.

You Tube will give lots of instruction videos if you still nervous.

The secret to strength.
Is to roll as much rosin out of area as you can..
Then brush back over job with a little more Rosin.

lay next cover of mat, and roll that in.

You can buy special rollers for it at fibreglassers.
But we've normally made our own.
Short\small Paint roller handle. Handfull of washers, centres to suit.
two different outer dia's.
Stack along short end of handle, large\small dia alternately.
with lock tab on end. Make sure they roll free.

That will roll out the job nicely.
But it's a one off unless you have some acetone, Thinners.


I always start or finish. Or both. with a layer of cloth and\or tape.
It's stronger than the mat. That's just basically the filler.

If roof really thick in depth.
Get some Talcum powder.
and mix in with rosin for a denser filler.

If thicker again.
Get some ply and clear plastic for inside,

Nah.

Send email I'll send you an instruction from mate

who builds
epairs large glass boats for 50 yrs.

He glassed my first yacht in '64ish..

The most important thing though.

is rolling as much out as you can. 

If Rosin too thick. lay up a coupla layers of mat\tape

rolling t'ween 'em to soak it up.

Till You can see the tape? clearly.

Then as he said. as it starts to gel.

Top coat with a layer. add white filler if you want color.

Brush, Let it run itself out. and sand after dinner or in morn.

One thing we have done LOTS of with boats.

Is play with fillers and rosin even the steel yachts.

My 34 fter was faired smooth from Waterline  to gun whales.

Around 50 kg of it.

That was a lot of long board fairing. Good for shoulders.

Back in '83., launched '85.

 NOT.... By me, I bought her floating in '94.

Hmm Could be more than you bargained for.
Depending on roof assembly.
Could be easier to remove inner skin or parts of.
Insert some decent "timber? crossbraces to flex outer skin up and replace inner.
7plus ft width, would have fair flex there normally.
Hence cause more trouble\damage than it's worth.

Have a word with somebody who knows THAT roof b4 committing.

PS.

How deep is the "well" in centre. and central to roof or front\back more.

If deep roof probably better way is to get some timber crossrails made up.

then fit side to side across roof.

below or  flush on sides. level or slightly proud at centre to give run off???.

Also depends on inner liner composition.

Lots of ways.

If you don't know what you doing or mix incorrectly. you could find your "top hat" External centre piece, glued on roof. 

"toffing itself" to some passing veh's.