I can only speak for what i have done. I have yet to do a 21" spoke, but have done 19" many times.
I am not sure if this helps, but I can tell you that the front wheel on the 19" is a real pain to do compaired to the rear.
I would place the rim on the bench then place a 2" block of wood under the hub lifting it up just a bit with all the spokes in the hub (all 40, both sides, keeping the ones on the down side of the hub out of your way) and the ones on the top of the hub held up in the air in a sphere shape with something like a roll of duct tape or simular to hold them together, not taped together, just from flopping down. then start with a hole on the rim and start working my way around following the pattern. This may take some twisting of the rim carefully, but after a few minutes is you pay close attention you will see the pattern develope and then keep going. now flipping the rim over is a pain in the butt, but if done carefully you can do it. Then repeat this process. When I screw on the nipples i do them just barely until the entire rim is laced, then slowly work my way around to each one, slowly turning each in a bit at a time until they are all snug.
Again, not sure this will help but just trying to help. Wished i had a 21" rim to try out.

 

Indeed, Joe.... It's primarily a dirt bike shop....Family has been in the business for years

Bettencourts in W. Bridgewater, MA

 

They want to charge me 158.00 to lace and true one wheel! ....and they're not even sure they'll do it right...???

I'm packaging these up and sending them out to HDwheels.... 80.00 per wheel, and no fuss.

 

So I'm getting ready to ship these out to HDwheels for lacing and truing, and I get a thought:

What if I lace up the rear wheel? I can't go wrong with that. It's the same hub and rim. If I make a mistake, I know it's me that's made it and not because I have the wrong hub or something.

So, I unpack the rear wheel parts... and go to work.... And I get the thing laced after 2 tries.

Now, I realized a critical thing in the process... The spokes are NOT supposed to actually reach the rim. You're supposed to put the nipple through the rim so that it'll grab and screw onto the spoke that appears to be just out of reach. So, alas, I get the thing laced.

Then, I thinking... Let me apply the same technique to the front wheel... And voila!... I get thing laced on first attempt.

=-) ....wheels are together!

So, I take them down to local Harley dealership where they told me previously that they would true them for me... So I drop them off and 4 days expire... I decide to give them a call when they tell me that they can't true them because of the 'old' truing stand that they have. They said they couldn't do it for the newer spoked wheels?

I'm like...???

Anyway, I'm going to pick them up and will find another place to have them trued. Weird a dealership wouldn't have a 'modern' truing stand. I asked her if she was sure it wasn't an issue with how they'd been laced. And she assured me that it wasn't and that everything was fine, but that their truing stand was a little dated.

Oh well. At least I know they're laced properly... Gotta find a place to true them, though.

 

dammit what a hassle!!

 

Perewitz is right down the street... I should have just taken them there in the first place. He's gonna take of me.

 

After I powdercoated my rims and hubs I had both wheels trued after I relaced them myself ... I jacked them both up the first time by getting the rims on backward (i.e., the stem facing the left side of the bike) ... took 'em back and reversed the rim and relaced them ...

It was kind of a pain in the **** lacing them as the second side of the wheel always gets pretty tight as you get the spokes on ....

I think the cost of having the wheels trued and balanced was about $150 ... 2 hours of shop time at $75/hr ....

Seems like that was just a bit much, but they did a good job and I have a lot of confidence in the indy shop that did it for me ....

R/
Priest