Correct method to join fibreglass panels

[tropicrows]

I have two section of fibreglass which a need to butt up against each other and join. I was going to use polyester resin with 4 layers 450gm CSM on the un-seen side. Then I was going to grind out the front joint line to about 20 mm wide x 1 mm deep and fill this with epoxy filler.
Is this suitable method or should I be adding some reinforcement to the front side as well before filling, or should I be doing the whole job differently. The last thing I want is a cosmetic crack appearing at a later date. All advise appreciated.

[Herman]

If you do not want the crack to appear, beef up the rear side as you suggest, then grind out the front, tapered 1:8 or even 1:12 and replace the lost glass nicely. Sand smooth, re-gelcoat or paint.

[rwatson]

Bit of a knowledge gap here.

What kind of pressures are going to be applied to the panels - are we talking structual hull, inner shell, deck, cuboard doors ,8x4, 6inches by 18inches

Thickened epoxy might be enough for some applications.

[Landlubber]

Whatever the use, herman has it about right anyhow.

[Herman]

Failing to taper the repair, which it is basicly, will always make the crack re-appear.

[rwatson]

It wouldnt be enough for exterior hull with high loadings - you would need inner and outer laminations, and not just of chopped mat either.

[tropicrows]

Thanks Herman,
the joint in on the inner shell in the deck area. I will go with the 1:8 tapper fill with glass and then finish with epoxy filler.