Anyone out there tried a Lascal Buggyboard on a Britax B-Dual?

[MrsHelenBee]

Hi everyone,

I really want some advice regarding a suitable buggyboard for a Britax B-Dual buggy.
I use a B-Dual for DS2, who is 16m.
DS1 is 4, chronically hypermobile and has Hypotonia. He didn't walk until 33m, only a couple of weeks before DS2 was born, and was not far off the weight limit for the additional B-Dual seat by then, so I had to push him when we were out and about, rather too far IMHO.
He still gets incredibly tired, making day-to-day errands hard work for him, and he's just started school too, which is utterly exhausting him, and the walk home at the end of the day is clearly a huge issue.
While he needs to pushed to a point to help strengthen muscle and joints, I know I'm going beyond his limits, and his physio and OT have both suggested a buggy board. Scooters and bikes are totally beyond him and not an option at all.
When DS2 was born, we had a different buggy and purchased the buggyboard thinking we'd found the solution. It was the worst £50 we'd ever spent, as the board stood back from the buggy so far that I was bent double trying to push. It wasn't just me, my husband couldn't get on with it either. We're both tall, but I've seen people out and about with all manner of buggies and attached boards who are able to push their kids around easily and comfortably, so they must vary hugely.
I've heard the Lascal fits the B-Dual, but I'm reluctant to spend £45-£65 again if I'm going to find the same problem. I don't know anyone with a B-Dual and board to be able to try it out or ask how well they get on with it. Added to which, Mothercare can order one in for me but I can't try it out in the store first as I've been told the pack contains special tape, which has to be applied to the buggy frame before the board's fitted, and then can't be used again, so I've got to buy the board and take the risk.
I've also heard people saying they were told their buggy warranty was invalidated after they attached the board, and while I've no reason to expect issues with the buggy, that's a bit of a worry.
DS1's physio and OT suggested I get a special needs buggy for him but, even if I wanted to go down that route (which I don't), DS2 is only 16m and needs a buggy, so how they think I'd be capable of pushing two buggies is beyond me.
DS1 needs help, and I love the idea of the board in theory.
anyone out there used it? How did you get on? Apart from being smaller and cheaper, are there any other differences between the Lascal Buggyboard and the Lascal mini? Can they both hold children up to the 20kg limit I've seen on the main board?

Sorry for the long message, but desperately want people's honest reviews.