Need your input on this idea...

Okay if you can do ALL the red with decals.  The big problem comes if you do not have a color calibrated printer.  Matching the color of paint and printer ink in homemade decals can be a real pain. One compromise is a decal that does the thin black stripe and a broader stripe of red, to ease the accuracy needed in designing the decal and the masking.  That way you do not need to be perfect.

What I have done sometimes with home-made decals is to print out a copy on regular paper and cut out the paper to use as a stencil for masking. I have sometimes put down masking tape first, then taped that stencil over the masking tape, mark the demarkation line with a pen, then cut out the masking tape with a really sharp knife.

Oh, thank heaven, I thought you were going to do some thing complex

Sorry I'll go be quiet over here in this corner  

But on a bit more serious note:  after you put down the black decal, as discussed above, you may want to apply a clear coat over the decal to minimize the "step" between the black decal and the application of the red paint coat. That may help minimize the telegraphing of the decal edge in the red field. Of course it will prolong your paint schedule, waiting for the clear to dry, so you may feel free to ignore the step as you wish.

Or, you might go with a pen, but prepare a template to go along, so your hand wouldn't have to be that steady - I've seen them do something like that (on TV) at the Harley Davidson plant to pinstripe the fuel tank for their bikes - that pinstriping went really fast! Hope it helps, have a nice day

Paweł

Steve, I most definitely will be clear-coating - not just for surface evenness but more importantly, to keep the decal from getting most surely pulled right off from masking for the red. Could you define "telescoping" a little bit? I am not a dumb guy and can usually figure out things like that but this time I am a little bit stumped on what exactly that is. 

Would I be better off using the exact same template for paint as well as the decal, and laying down the red first and THEN the black stripe, then touching up after to hide any gaps between the red/black? I just figured doing the black first just meant that I could mask using the black pinstripe as a guide to eliminate paint/mask/template errors. 

Pawel, you definitely have a good point but I don't feel like I will be able to pull that off well - I think I am going to go with the decal, but thank you for your input!

"...keep the decal from getting most surely pulled right off from masking for the red. Could you define "telescoping" a little bit? I am not a dumb guy and can usually figure out things like that but this time I am a little bit stumped on what exactly that is. ...." 

I  never thought of you as dumb; Sorry,  sometimes my thoughts get ahead of my finger speed and I don't notice if I caused some confusion or use some arcane term (I'm pretty arcane myself so I sometimes talk funny to you younger folks)

The Idea of the "telegraphing" is that, in this case, the edge of one decal under another would create a double thickness at the overlap, this would result in a "bump" . Thus the bottom decal edge would "telegraph" (ie show) its edge though the top layer at that location.

A poor drawing to illustrate  (also proving I still cant spell that darn word)

Makes perfect sense. So basically what you were trying to say was not having a clear coat may mean we'd see the edge of the black decal beneath the red on top. See I gots da smarts, yo!

Now my question is... how much time did you spend making that cute little illustration? 

The thickness of decal film is getting so thin in latest kits that it should minimize the problem.  Love the newer decals, except I have to force myself to always apply the decal by placing it next to desired location while still on backing sheet and slide it over.  The days of picking up a decal with tweezers off the sheet and applying it to the model seem to be over. If a decal folds back upon itself, it is done for these days!