Por-15's Power Mesh product should work well for this. It's a fiberglass mesh that is used in conjunction with Por-15 paint instead of resin. It's used to seal holes too large for Por-15's putty.
I used both in repairing my cab's floor pan.
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Bob
2005 E350 Super Duty Ext Wheelchair Van
2002 Itasca 35U Motorhome
Linear Mode
