Why not just pack the data into a scalar and pass that to your XS?

#! perl -slw
use 5.010;
use strict;
use Inline C => Config => BUILD_NOISY => 1;
use Inline C => <<'END_C',  NAME => 'junk', CLEAN_AFTER_BUILD => 0;

void test( SV *in ) {
     size_t len  =       SvCUR( in ), i;
     U32    *ary = (U32*)SvPVX( in );

    for( i = 0; i < len / sizeof(U32); ++i ) {
        printf( "%d:%d\n", i, ary[ i ] );
    }
    return;
}

END_C

my $ary = pack 'V*', 1 .. 20;

test( $ary );

__END__
C:\test>826865.pl
0:1
1:2
2:3
3:4
4:5
5:6
6:7
7:8
8:9
9:10
10:11
11:12
12:13
13:14
14:15
15:16
16:17
17:18
18:19
19:20
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