Xai-xai to Giriyondo border for Kruger

Your main problem will be the border at Giryondo - it closes at 16:00 and not at the same time as the other park entrance gates. Although you might make it from Xai-Xai to Letaba (via Macia, Chokwe and Giryondo) in one day I would not rely on doing so.
You could easily make it from Maputo to the Kruger entrance gate at Crocodile Bridge in a few short hours - it is less than 100km, but the border crossing at Ressano Garcia hold you up, especially over week-ends. However, there is no way that you will then make it up to Letaba the same day.
Unless you have another day in hand, I would not recommend that you try to get to Letaba and would instead suggest that you change your accommodation reservation within the park to either Crocodile Bridge or Lower Sabie.

I agree with the above. We travelled from Mopani via Giriyondo to Bilene in September. There is about a 100km stretch of what was bad bitumen which is now almost completely dug up and you are reduced to driving on dirt tracks next to the roadworks at 25kph on and off for ages. We left at about 7 30 a.m and got to Bilene about 3.30pm with only stop at the border. It was so tedious that instead of my plan to come back that way to Phalaborwa we went all the way around to Maputo and Komatipoort and stayed a night in Berg n dal (couldn't get in at Crocodile Bridge as it was full). This also took ages we left at 1.30pm and got to park gate after closing at 7pm. Roadworks in Maputo before the border turn off had traffic at a crawl for a long time. The lesson is that what looks perfectly feasible on the map can take a lot longer in reality with unexpected hold ups occurring. Whatever you decide remember that from November 1st you cannot use Giriyondo as a through road in/out of Kruger unless you have at least one night booked in Kruger but it looks like you have that covered anyway.

"from November 1st you cannot use Giriyondo as a through road in/out of Kruger unless you have at least one night booked in Kruger"
Very interesting, Threedogs. I was not aware of that constraint. I hope they implement the same rule at the Pafuri border crossing.

Thanks so much for these words of wisdom. That is very helpful.
I think we will try and get into the park at Crocodile Bridge early in the morning and work our way up to Leteba in the park. Do you think the journey from Crocodile Bridge entrance to Leteba is do-able in a day, bearing in mind the speed limit and a few animal sightings!?
Thanks again
Hannah

If you get to Crocodile Bridge at about 06:30 then some people might consider it doable. I am not one of them. The speed limit on tar roads (which you will be using) is 50 kph. You will see animals - more than you expect to see - and you will want to spend time watching them. There is no point in going to Kruger if you do not want to spend time watching Elephants, Lions, etc. And you would be surprised at how much time that eats up. You would be unlucky if you could average as much as 25 kph. Letaba is 199 km from Crocodile Bridge - that is a good 8 hours drive. Add to that the time that you would want to spend having breakfast and lunch and P breaks and T breaks. And that through the heat of December. Not for me, thank you.
Change your reservation to a camp further south.

@number 3
I believe it will apply to Parfuri border crossing as well. There are apparently negotiations to try to get the park authorities on the Moz side to implement a similar rule. ie a one night stay in the Limpopo park. This has been enforced now due to pressure from concerned park visitors and others that the cross border routes via the parks are being used as a short cut thoroughfare when that was not the intended use. In addition to the one night stay rule, they are also supposed to start enforcing the rule that no commercial vehicles will be allowed through either.

Fantastic. That would certainly curb the traffic speeding along the tar road from Pafuri entrance gate to the Pafuri border post. However, I foresee a problem because the only Parks Board camp in the vicinity is Punda Maria - and that is a good 1 1/2 to 2 hours from the border post.

Thanks very much