Not sure what you mean by “using a dab of cheater lam around the lap line” but (using a sanding block and a coarse grit) I hand sand the edge close to flush but not quite then baste the edge first (under the glass) when glassing
i too read somewhere someone (with MUCH more skill than i) wrote about not grinding laps… i tried it on my 4th or 5th glass job and: bubble-city!
don’t do it! you want to take your time and prep those laps as best you can… i still have the a-board-shun laying around to remind me to always prep the laps.
If you want to skip the grinding of the lap on a CUT lap - you can take a seam roller or tounge depresser and press the edge of the lap flush with the foam.
You are not going to want to just cut the lap and do nothign with it. Not only will you probably get a tun of bubbles but when you go back to sand your hot coat your gonna get a ton of sand through and probably a hand full of spots where you sand through your top layer of glass in order to get everything smooth.
You could also cut the lap and baste the edge with clear resin but you would still probably need to sand that out flush a bit for the best results. - This would not be a good idea if you are using any color on your deck - all in all sounds like more work to me.
If you have a clean cut lap to start with, I would go the seam roller route. Really works good, especially if you have a good metal seam roller. You can really get a good amount of pressure on the lap line and make a really smooth transition.
If you tape, mask, and cut the lap, and probably not too much glass, then the roller may be good. I free lap at least three layers, I try to get each outer layer a little longer, I start with the bottom, and I am not very concerned with how it looks.
I think the main point is to have a flush surface for the next lam.
I cut lap in a vaccum bag. Keep a scrap of wetted out cloth outside the bag. When it isn’t stickey anymore, neither is the board. Rubbery laps are so easy to cut clean. Vacuum makes it so tight, just glass over it on the next layer
I generally lap the first layers (top and bottom) at least a couple inches around. Subsequent layers can end elsewhere, IMO, depending on what you’re doing, how many layers, etc.
You should sand the lap. It will help to have that as flat as possible for your final sand to go well.
The first layer should be cut anywhere from the apex of the rail down to bottom of the rail.
Just ride your scissors right on the rail. You can cut from center out and you won’t get straggle strings.
Each step is important to have a clean finished board and make sanding easier on you. If you lap both layers you will have a lump, and then sand through, and then need a cheater and a second hotcoat etc. Same applies to knocking the lap down in the first place.